Prospectus Filed Pursuant to Rule 424(b)(5) (424b5)

DESCRIPTION OF COMMON STOCK AND PREFERRED STOCK

        The following description of our common stock and preferred stock, together with any additional information we include in any applicable prospectus supplement or any related free writing prospectus, summarizes the material terms and provisions of our common stock and the preferred stock that we may offer under this prospectus. While the terms we have summarized below will apply generally to any future common stock or preferred stock that we may offer, we will describe the particular terms of any class or series of these securities in more detail in the applicable prospectus supplement or free writing prospectus. For the complete terms of our common stock and preferred stock, please refer to our amended and restated certificate of incorporation (as amended), which we refer to herein as our certificate of incorporation, and our amended and restated bylaws, which we refer to herein as our bylaws, copies of which are filed with the SEC. The terms of these securities may also be affected by the Delaware General Corporation Law, or the DGCL. The summary below and that contained in any applicable prospectus supplement or any related free writing prospectus are qualified in their entirety by reference to our certificate of incorporation and our bylaws. See "Where You Can Find Additional Information."

Authorized Capital

        Our authorized capital stock consists of 750,000,000 shares of common stock, par value $0.01 per share, and 5,000,000 shares of preferred stock, par value $0.01 per share.

Common Stock

        As of September 30, 2019, 253,121,439 shares of our common stock were issued and outstanding (excluding 861,139 treasury shares). In addition, as of September 30, 2019, there were: (i) 23,597,871 shares of common stock issuable upon the exercise of stock options at a weighted average exercise price of $2.44 per share; (ii) 4,333,560 shares of common stock issuable upon the vesting of restricted stock units; (iii) 115,824,142 shares of common stock issuable upon exercise of warrants; (iv) 2,782,076 shares of common stock issuable upon conversion of our Series C Redeemable Convertible Preferred Stock at a conversion price of $0.2343 per share; (v) 12,237,762 shares of common stock issuable upon conversion of our Series E Convertible Preferred Stock at a conversion price of $2.31 per share; (vi) 43,630,020 shares of common stock issuable upon conversion of our 5.5% Convertible Senior Notes due March 15, 2023 at a conversion price of $2.29 per share ; (vii) 15,503,876 shares of common stock issuable upon conversion of our 7.5% Convertible Senior Note due January 2023 at a conversion price of $2.58 per share; and (viii) 8,373,467 shares of our common stock reserved for future issuance under our equity incentive plans. Additional shares of authorized common stock may be issued, as authorized by our board of directors from time to time, without stockholder approval, except as may be required by applicable securities exchange requirements.

        The holders of common stock possess exclusive voting rights in us, except to the extent of such rights reserved to holders of our Series C Redeemable Convertible Preferred Stock and Series E Convertible Preferred Stock and to the extent our board of directors specifies voting power with respect to any other class of securities issued in the future. Each holder of our common stock is entitled to one vote for each share held of record on each matter submitted to a vote of stockholders, including the election of directors. Stockholders do not have any right to cumulate votes in the election of directors.

        Subject to the preferences that may be applicable to any then outstanding preferred stock, each holder of our common stock is entitled to share ratably in distributions to stockholders and to receive ratably such dividends, if any, as may be declared from time to time by our board of directors out of legally available funds. In the event of our liquidation, dissolution or winding up, holders of our common stock will be entitled to share ratably in the net assets legally available for distribution to

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stockholders after the payment of all of our debts and other liabilities, subject to the satisfaction of any liquidation preference granted to the holders of any outstanding shares of preferred stock (including the Series C Redeemable Convertible Preferred Stock and Series E Convertible Preferred Stock).

        All of the outstanding shares of our common stock are, and the shares of common stock issued upon the conversion of any securities convertible into our common stock will be, duly authorized, fully paid and nonassessable. Holders of our common stock have no preemptive, conversion or subscription rights, and there are no redemption or sinking fund provisions applicable to our common stock. The rights, preferences and privileges of the holders of our common stock are subject to, and may be adversely affected by, the rights of the holders of the Series C Redeemable Convertible Preferred Stock and Series E Convertible Preferred Stock as well as the rights of any series of our preferred stock that we may designate and issue in the future.

        Our common stock trades on the NASDAQ Capital Market under the symbol "PLUG."

Preferred Stock

        As of September 30, 2019, 2,620 shares of Series C Redeemable Convertible Preferred Stock, par value $0.01 per share ("Series C Preferred Stock"), and 28,269 shares of Series E Convertible Preferred Stock, par value $0.01 per share ("Series E Preferred Stock"), were issued and outstanding. The Company has authorized Series A Junior Participating Cumulative Preferred Stock, par value $0.01 per share. As of September 30, 2019, there were no shares of Series A Junior Participating Cumulative Preferred Stock issued and outstanding.

        The Company's certificate of incorporation authorizes its board of directors to classify any unissued shares of preferred stock and to reclassify any previously classified but unissued shares of any series into other classes or series of stock. We may issue preferred stock from time to time in one or more class or series, with the exact terms of each class or series established by our board of directors. Prior to the issuance of shares of each class or series of preferred stock, the Company's board of directors will set the terms, preferences, conversion or other rights, voting powers, restrictions, limitations as to dividends or other distributions, qualifications and terms or conditions of redemption for each such class or series.

        The preferences and other terms of the preferred stock of each class or series will be fixed by the certificate of designation relating to such class or series. We will incorporate by reference into the registration statement of which this prospectus is a part the form of any certificate of designation that describes the terms of the series of preferred stock we are offering before the issuance of the related series of preferred stock. The applicable prospectus supplement will specify the terms of the preferred stock, including, where applicable, the following:

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the title and stated value;



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the number of shares we are offering;



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the liquidation preference per share;



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the purchase price;



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the dividend rate, period and payment date and method of calculation for dividends;



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whether dividends will be cumulative or non-cumulative and, if cumulative, the date from which dividends will accumulate;



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the procedures for any auction and remarketing, if any;



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the provisions for a sinking fund, if any;

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the provisions for redemption or repurchase, if applicable, and any restrictions on our ability to exercise those redemption and repurchase rights;



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any listing of the preferred stock on any securities exchange or market;



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whether the preferred stock will be convertible into our common stock, and, if applicable, the conversion price, or how it will be calculated, and the conversion period;



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whether the preferred stock will be exchangeable into debt securities, and, if applicable, the exchange price, or how it will be calculated, and the exchange period;



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voting rights, if any, of the preferred stock;



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preemptive rights, if any;



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restrictions on transfer, sale or other assignment, if any;



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whether interests in the preferred stock will be represented by depositary shares;



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a discussion of any material United States federal income tax considerations applicable to the preferred stock;



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the relative ranking and preferences of the preferred stock as to dividend rights and rights if we liquidate, dissolve or wind up our affairs;



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any limitations on the issuance of any class or series of preferred stock ranking senior to or on a parity with the series of preferred stock as to dividend rights and rights if we liquidate, dissolve or wind up our affairs; and



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any other specific terms, preferences, rights or limitations of, or restrictions on, the preferred stock.

        Unless otherwise specified in the applicable prospectus supplement, the preferred stock will, with respect to dividend rights and rights upon liquidation, dissolution or winding up of the Company, rank: (i) senior to all classes or series of the common stock, and to any other class or series of the Company's stock expressly designated as ranking junior to the preferred stock; (ii) on parity with any class or series of the Company's stock expressly designated as ranking on parity with the preferred stock; and (iii) junior to any other class or series of the Company's stock expressly designated as ranking senior to the preferred stock.

        The DGCL provides that the holders of preferred stock will have the right to vote separately as a class (or, in some cases, as a series) on an amendment to our certificate of incorporation if the amendment would change the par value, the number of authorized shares of the class or the powers, preferences or special rights of the class or series so as to adversely affect the class or series, as the case may be. This right is in addition to any voting rights that may be provided for in the applicable certificate of designation.

        Our board of directors may authorize the issuance of preferred stock with voting or conversion rights that could adversely affect the voting power or other rights of the holders of our common stock. The issuance of preferred stock, while providing flexibility in connection with possible acquisitions and other corporate purposes, could, among other things, have the effect of delaying, deferring or preventing a change in our control and may adversely affect the market price of the common stock and the voting and other rights of the holders of common stock. Additionally, the issuance of preferred stock may have the effect of decreasing the market price of our common stock.

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Series C Redeemable Convertible Preferred Stock

        In May 2013, 10,431 shares of Series C Preferred Stock were issued at the original issue price of $248.794 per share, of which 2,620 shares remain outstanding as of September 30, 2019. The Company's board of directors approved the certificate of designation, a copy of which has been previously filed with the SEC and which is incorporated by reference as an exhibit to the registration statement of which this prospectus is a part, creating the Series C Preferred Stock. The following description of the Series C Preferred Stock is qualified in its entirety by reference to such certificate of designation and the Company's certificate of incorporation. The Series C Preferred Stock is validly issued, fully paid and nonassessable.

        Ranking.    The Series C Preferred Stock ranks, with respect to dividend rights and rights upon the Company's liquidation, dissolution or winding up, senior to all classes or series of the common stock and to any other class or series of stock expressly designated as ranking junior to the Series C Preferred Stock, including the Series E Preferred Stock.

        Dividends.    The Series C Preferred Stock is entitled to receive dividends at a rate of 8% per annum, based upon the original issue price, payable in equal quarterly installments, in preference to common stock and other junior securities, in cash or in shares of common stock, at our option. The Series C Preferred Stock is convertible into shares of our common stock, at a conversion price equal to $0.2343 per share (as of September 30, 2019 and subject to future adjustments), at the holder's option. As of September 30, 2019, the outstanding shares of our Series C Preferred Stock were convertible into an aggregate of 2,782,076 shares of our common stock. The Series C Preferred Stock has weighted average anti-dilution protection.

        Conversion Rights.    The holders of Series C Preferred Stock have the right, at their sole option, to convert the Series C Preferred Stock into shares of common stock at a conversion price in effect at the time of conversion; provided that such conversion price shall not be less than $0.1554 per share. The Series C Preferred Stock may also be automatically converted at the then effective conversion rate upon the election by holders of at least 67% of the outstanding shares of Series C Preferred Stock under certain circumstances.

        Redemption Rights.    The Series C Preferred Stock is redeemable by the Company upon the election of either the holders of the Series C Preferred Stock or us. If the redemption is at the election of the holders of the Series C Preferred Stock, the redemption price will be the original issue price plus any accrued and unpaid dividends. If the redemption is at the election of the Company, the redemption price will be a per share price equal to the greater of (i) the original issue price per share plus any accrued and unpaid dividends and (ii) the fair market value of a single share of Series C Preferred Stock.

        Voting Rights.    The shares of Series C Preferred Stock vote together with the common stock on an as-converted basis on all matters, including the election of directors, except as otherwise required by law. Each share of Series C Preferred Stock is entitled to a number of votes equal to the number of whole shares of common stock into which such share of Series C Preferred Stock is convertible.

Series E Convertible Preferred Stock

        In November 2018, 35,000 shares of Series E Preferred Stock were issued at the initial stated value of $1,000 per share, of which 28,269 shares remain outstanding as of September 30, 2019. The Company's board of directors approved the certificate of designation, a copy of which has been previously filed with the SEC and which is incorporated by reference as an exhibit to the registration statement of which this prospectus is a part, creating the Series E Preferred Stock. The following description of the Series E Preferred Stock is qualified in its entirety by reference to such certificate of designation and the Company's certificate of incorporation. The Series E Preferred Stock is validly issued, fully paid and nonassessable.

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        Maturity Date.    The Series E Preferred Stock will mature on May 2, 2020, unless extended at the option of the holders of the Series E Preferred Stock.

        Ranking.    Except for the Series C Preferred Stock, the Series E Preferred Stock ranks, with respect to dividend rights and rights upon the Company's liquidation, dissolution or winding up, senior to all classes or series of the common stock and to any other class or series of stock expressly designated as ranking junior to the Series E Preferred Stock. In the event of a liquidation, dissolution or winding up of the Company, the holders of Series E Preferred Stock will be entitled to receive in cash out of the Company's assets after any amount that is required to be paid to the Series C Preferred Stock and before any amount shall be paid to the holders of any of capital stock ranking junior to the Series E Preferred Stock, but pari passu with any capital stock then outstanding that ranks pari passu with the Series E Preferred Stock, an amount per share equal to the greater of (A) 125% of the conversion amount and (B) the amount per share such holder would receive if such holder converted such shares into common stock immediately prior to the date of such payment.

        Dividends.    The Series E Preferred Stock is not entitled to receive dividends, except in connection with certain purchase rights and other corporate events, as described in the certificate of designation, or in connection with certain distributions of assets, as described in the certificate of designation, or as, when and if declared by the board of directors acting in its sole and absolute discretion.

        Optional Installment Conversion or Redemption by the Company.    On the first trading day of each calendar month commencing on May 1, 2019 and through, and including, April 1, 2020, and on the maturity date (each an "Installment Date"), provided that all conditions set forth in the certificate of designation have been satisfied, the Company will convert an amount equal to $2,693,000 in stated value of the Series E Preferred Stock (as such amount may be reduced by earlier conversion, redemption or otherwise) into shares of common stock at the greater of (x) $0.55 and (y) the lowest of (i) the conversion price then in effect and (ii) 85% of the average volume weighted average price, or VWAP, of the common stock for the three lowest trading days during the seven consecutive trading day period immediately prior to the applicable Installment Date; provided, however, that the Company may instead, at its option, pay such amount by redeeming shares of Series E Preferred Stock for cash at the applicable redemption price. If the equity conditions are not satisfied, then any holder of the Series E Preferred Stock may require the Company to redeem the conversion amount at 125% of such designated portion of the conversion amount.

        Mandatory Conversion by the Company.    The Company has the right, provided that no equity conditions failure exists, to require each holder of Series E Preferred Stock to convert all or any number of shares of Series E Preferred Stock held by such holder at the conversion rate if the closing sale price of our common stock equals at least 175% of the conversion price for twenty consecutive trading days.

        Optional Conversion by the Holders.    The holders of the Series E Preferred Stock are entitled to convert any whole number of shares of Series E Preferred Stock into shares of common stock at the conversion price of $2.31, subject to adjustments.

        Maturity Redemption by the Holders.    At any time from and after the tenth business day prior to the maturity date, any holder may require the Company to redeem all or any number of shares of Series E Preferred Stock held by such holder at a purchase price equal to 105% of the conversion amount.

        Redemption/Conversion Option of the Holders upon a Triggering Event.    After a triggering event (as described in the certificate of designation), each holder will have the right, at such holder's option, to require the Company to redeem and/or convert all or a portion of such holder's Series E Preferred Stock. Any such redemption would be at a price per share equal to the greater of (i) 120% of the

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conversion amount and (ii) the product of (A) the conversion rate in effect multiplied by (B) 120% of the greatest closing sale price of the common stock on any trading day during the period specified in the certificate of designation. Any such triggering event conversion would be at a conversion rate equal to the quotient of (i) 120% of the conversion amount divided by (ii) the lower of (A) the applicable conversion price in effect on the trading day immediately preceding the notice of conversion and (B) the greater of (1) $0.55 and (2) 75% of the lowest VWAP of the common stock on any trading day during the period specified in the certificate of designation.

        Redemption Right of the Holders Upon a Change of Control.    In the event of a fundamental transaction, as described in the certificate of designation, generally including, among other transactions, any merger with or into another entity in which the Company is not the surviving entity or the Company's stockholders immediately prior to such merger or consolidation do not own at least 50% of the outstanding voting securities of the surviving entity, or a sale of all or substantially all of the Company's assets, each holder will have the right, at such holder's option, to require the Company to redeem all or a portion of such holder's Series E Preferred Stock. Any such change of control redemption would be at a price per share equal to 125% of the greatest of (i) the conversion amount being redeemed, (ii) the product of (A) the conversion amount being redeemed multiplied by (B) the quotient determined by dividing (1) the greatest closing sale price of the common stock during the period specified in the certificate of designation by (2) the conversion price, and (iii) the product of (A) the conversion amount being redeemed and (B) the quotient determined by dividing (1) the aggregate cash consideration and the aggregate cash value of any non-cash consideration per share of common stock to be paid to holders of the common stock upon consummation of such change of control by (2) the conversion price.

        Voting Rights.    The shares of Series E Preferred Stock have no voting rights, except on matters required by law or under the certificate of designation to be submitted to a class vote of the holders of the Series E Preferred Stock.

Delaware Anti-Takeover Law and Provisions of our Certificate of Incorporation and Bylaws

        Delaware Anti-Takeover Law.    We are subject to Section 203 of the DGCL. Section 203 generally prohibits a public Delaware corporation from engaging in a "business combination" with an "interested stockholder" for a period of three years after the date of the transaction in which the person became an interested stockholder, unless:

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prior to the date of the transaction, the board of directors of the corporation approved either the business combination or the transaction which resulted in the stockholder becoming an interested stockholder;



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the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the number of shares outstanding (a) shares owned by persons who are directors and also officers and (b) shares owned by employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or



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on or subsequent to the date of the transaction, the business combination is approved by the board and authorized at an annual or special meeting of stockholders, and not by written consent, by the affirmative vote of at least two-thirds of the outstanding voting stock which is not owned by the interested stockholder.

        Section 203 defines a business combination to include:

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any merger or consolidation involving the corporation and the interested stockholder;

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any sale, transfer, pledge or other disposition involving the interested stockholder of 10% or more of the assets of the corporation;



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subject to exceptions, any transaction that results in the issuance or transfer by the corporation of any stock of the corporation to the interested stockholder; and



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the receipt by the interested stockholder of the benefit of any loans, advances, guarantees, pledges or other financial benefits provided by or through the corporation.

        In general, Section 203 defines an interested stockholder as any entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation or any entity or person affiliated with or controlling or controlled by the entity or person.

        Certificate of Incorporation and Bylaws.    Provisions of our certificate of incorporation and bylaws may delay or discourage transactions involving an actual or potential change in our control or change in our management, including transactions in which stockholders might otherwise receive a premium for their shares or transactions that our stockholders might otherwise deem to be in their best interests. Therefore, these provisions could adversely affect the price of our common stock. Among other things, our certificate of incorporation and bylaws:

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permit our board of directors to issue up to 5,000,000 shares of preferred stock, with any rights, preferences and privileges as they may designate;



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provide that the authorized number of directors may be changed only by resolution of the board of directors;



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provide that all vacancies, including newly created directorships, may, except as otherwise required by law and subject to the rights of the holders of any series of preferred stock, be filled by the affirmative vote of a majority of directors then in office, even if less than a quorum;



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divide our board of directors into three classes;



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generally require that any action to be taken by our stockholders must be effected at a duly called annual or special meeting of stockholders and not be taken by written consent;



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provide that stockholders seeking to present proposals before a meeting of stockholders or to nominate candidates for election as directors at a meeting of stockholders must provide notice in writing in a timely manner, and also specify requirements as to the form and content of a stockholder's notice;



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do not provide for cumulative voting rights (therefore allowing the holders of a majority of the shares of common stock entitled to vote in any election of directors to elect all of the directors standing for election, if they should so choose); and



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provide that, except as otherwise required by statute and subject to the rights of the holders of any series of preferred stock, special meetings of our stockholders may be called only by the board of directors pursuant to a resolution adopted by a majority of the directors then in office.

        The amendment of any of these provisions, with the exception of the ability of our board of directors to issue shares of preferred stock and designate any rights, preferences and privileges thereto, would require approval by the holders of at least two-thirds of our then outstanding common stock.

DESCRIPTION OF WARRANTS

        We may issue warrants for the purchase of common stock, preferred stock and/or debt securities in one or more series. We may issue warrants independently or together with common stock, preferred stock and/or debt securities, and the warrants may be attached to or separate from these securities. The following description, together with the additional information we include in any applicable prospectus supplement or any related free writing prospectus, summarizes the material terms and provisions of the warrants that we may offer under this prospectus and the related warrant agreements and warrant certificates. While the terms we have summarized below will apply generally to any future warrants that we may offer, we will describe the particular terms of any series of warrants in more detail in the applicable prospectus supplement or free writing prospectus. The terms of any warrants offered under that prospectus supplement or free writing prospectus may differ from the terms described below. The following description and any description of the warrants in a prospectus supplement or free writing prospectus may not be complete and is subject to and qualified in its entirety by reference to the terms and provisions of the warrant agreement and warrant certificate, which we will file with the SEC in connection with an issuance of the warrants.

General

        We will evidence each series of warrants by warrant certificates that we will issue under a separate warrant agreement. We will enter into the warrant agreement with a warrant agent. We will indicate the name and address of the warrant agent in the applicable prospectus supplement relating to a particular series of warrants.

        We will describe in the applicable prospectus supplement the terms of the series of warrants, including:

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the offering price and aggregate number of warrants offered;



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the currency for which the warrants may be purchased;



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if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each such security or each principal amount of such security;



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if applicable, the date on and after which the warrants and the related securities will be separately transferable;



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in the case of warrants to purchase debt securities, the principal amount of debt securities purchasable upon exercise of one warrant and the price at, and currency in which, this principal amount of debt securities may be purchased upon such exercise;



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in the case of warrants to purchase common stock or preferred stock, the number of shares of common stock or preferred stock, as the case may be, purchasable upon the exercise of one warrant and the price at which these shares may be purchased upon such exercise;



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the effect of any merger, consolidation, sale or other disposition of our business on the warrant agreement and the warrants;



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the terms of any rights to redeem or call the warrants;



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any provisions for changes to or adjustments in the exercise price or number of securities issuable upon exercise of the warrants;



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the periods during which, and places at which, the warrants are exercisable;



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the manner of exercise;



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the dates on which the right to exercise the warrants will commence and expire;

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the manner in which the warrant agreement and warrants may be modified;



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federal income tax consequences of holding or exercising the warrants;



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the offering price and aggregate number of warrants offered;



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the terms of the securities issuable upon exercise of the warrants; and



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any other specific terms, preferences, rights or limitations of or restrictions on the warrants.

        Prior to the exercise of their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including the right to receive dividends, if any, or, payments upon our liquidation, dissolution or winding up or to exercise voting rights, if any.

Exercise of Warrants

        Each warrant will entitle the holder to purchase the securities that we specify in the applicable prospectus supplement at the exercise price that we describe in the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to the specified time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

        Holders of the warrants may exercise the warrants by delivering the warrant certificate representing the warrants to be exercised together with specified information, and paying the required amount to the warrant agent in immediately available funds, as provided in the applicable prospectus supplement. We will set forth on the reverse side of the warrant certificate and in the applicable prospectus supplement the information that the holder of the warrant will be required to deliver to the warrant agent.

        Upon receipt of the required payment and the warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will issue and deliver the securities purchasable upon such exercise. If fewer than all of the warrants represented by the warrant certificate are exercised, then we will issue a new warrant certificate for the remaining amount of warrants. If we so indicate in the applicable prospectus supplement, holders of the warrants may surrender securities as all or part of the exercise price for warrants.

Governing Law

        Unless we provide otherwise in the applicable prospectus supplement, the warrants and warrant agreements will be governed by and construed in accordance with the laws of the State of New York.

Enforceability of Rights by Holders of Warrants

        Each warrant agent will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of the related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, its warrants.

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DESCRIPTION OF DEBT SECURITIES

        We may issue senior debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. While the terms we have summarized below will apply generally to any future debt securities we may offer under this prospectus, we will describe the particular terms of any debt securities offered through that prospectus supplement or free writing prospectus. The terms of any debt securities we offer under a prospectus supplement or free writing prospectus may differ from the terms we describe below. Unless the context requires otherwise, whenever we refer to the "indentures," we also are referring to any supplemental indentures that specify the terms of a particular series of debt securities.

        We will issue any senior debt securities under the senior indenture that we will enter into with the trustee named in the senior indenture. We will issue any subordinated debt securities under the subordinated indenture that we will enter into with the trustee named in the subordinated indenture. We have filed forms of these documents as exhibits to the registration statement, of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

        The indentures will be qualified under the Trust Indenture Act of 1939, as amended, or the Trust Indenture Act. We use the term "trustee" to refer to either the trustee under the senior indenture or the trustee under the subordinated indenture, as applicable.

        The following summaries of material provisions of the senior debt securities, the subordinated debt securities and the indentures are subject to, and qualified in their entirety by reference to, all of the provisions of the indenture applicable to a particular series of debt securities. We urge you to read the applicable prospectus supplement or free writing prospectus and any related free writing prospectuses related to the debt securities that we may offer under this prospectus, as well as the complete applicable indenture that contains the terms of the debt securities. Except as we may otherwise indicate, the terms of the senior indenture and the subordinated indenture are identical.

General

        We will describe in the applicable prospectus supplement or free writing prospectus the terms of the series of debt securities being offered, including:

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the title;



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the principal amount being offered, and if a series, the total amount authorized and the total amount outstanding;



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any limit on the amount that may be issued;



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whether or not we will issue the series of debt securities in global form, and, if so, the terms and who the depository will be;



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the maturity date;



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whether and under what circumstances, if any, we will pay additional amounts on any debt securities held by a person who is not a United States person for tax purposes, and whether we can redeem the debt securities if we have to pay such additional amounts;



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the annual interest rate, which may be fixed or variable, or the method for determining the rate and the date interest will begin to accrue, the dates interest will be payable and the regular record dates for interest payment dates or the method for determining such dates;

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whether or not the debt securities will be secured or unsecured, and the terms of any secured debt;



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the terms of the subordination of any series of subordinated debt;



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the place where payments will be payable;



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restrictions on transfer, sale or other assignment, if any;



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our right, if any, to defer payment of interest and the maximum length of any such deferral period;



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the date, if any, after which, the conditions upon which, and the price at which, we may, at our option, redeem the series of debt securities pursuant to any optional or provisional redemption provisions and the terms of those redemption provisions;



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the date, if any, on which, and the price at which we are obligated, pursuant to any mandatory sinking fund or analogous fund provisions or otherwise, to redeem, or at the holder's option, to purchase, the series of debt securities and the currency or currency unit in which the debt securities are payable;



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whether the indenture will restrict our ability or the ability of our subsidiary to:



•

incur additional indebtedness;



•

issue additional securities;



•

create liens;



•

pay dividends or make distributions in respect of our capital stock or the capital stock of our subsidiary;



•

redeem capital stock;



•

place restrictions on our subsidiary's ability to pay dividends, make distributions or transfer assets;



•

make investments or other restricted payments;



•

sell or otherwise dispose of assets;



•

enter into sale-leaseback transactions;



•

engage in transactions with stockholders or affiliates;



•

issue or sell stock of our subsidiary;



•

effect a consolidation or merger;



•

whether the indenture will require us to maintain any interest coverage, fixed charge, cash flow-based, asset-based or other financial ratios;



•

a discussion of certain material or special United States federal income tax considerations applicable to the debt securities;



•

information describing any book-entry features;



•

provisions for a sinking fund purchase or other analogous fund, if any;



•

the applicability of the provisions in the indenture on discharge;

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•

whether the debt securities are to be offered at a price such that they will be deemed to be offered at an "original issue discount" as defined in paragraph (a) of Section 1273 of the Internal Revenue Code of 1986, as amended;



•

the denominations in which we will issue the series of debt securities, if other than denominations of $1,000 and any integral multiple thereof;



•

the currency of payment of debt securities if other than U.S. dollars and the manner of determining the equivalent amount in U.S. dollars; and



•

any other specific terms, preferences, rights or limitations of, or restrictions on, the debt securities, including any additional events of default or covenants provided with respect to the debt securities, and any terms that may be required by us or advisable under applicable laws or regulations or advisable in connection with the marketing of the debt securities.

Conversion or Exchange Rights

        We will set forth in the applicable prospectus supplement or free writing prospectus the terms on which a series of debt securities may be convertible into or exchangeable for our common stock, our preferred stock or other securities (including securities of a third-party). We will include provisions as to whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of our common stock, our preferred stock or other securities (including securities of a third-party) that the holders of the series of debt securities receive would be subject to adjustment.

Consolidation, Merger or Sale

        Unless we provide otherwise in the prospectus supplement or free writing prospectus applicable to a particular series of debt securities, the indentures will not contain any covenant that restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of all or substantially all of our assets. However, any successor to or acquirer of such assets must assume all of our obligations under the indentures or the debt securities, as appropriate. If the debt securities are convertible into or exchangeable for other securities of ours or securities of other entities, the person with whom we consolidate or merge or to whom we sell all of our property must make provisions for the conversion of the debt securities into securities that the holders of the debt securities would have received if they had converted the debt securities before the consolidation, merger or sale.

Events of Default Under the Indenture

        Unless we provide otherwise in the prospectus supplement or free writing prospectus applicable to a particular series of debt securities, the following are events of default under the indentures with respect to any series of debt securities that we may issue:

•

if we fail to pay interest when due and payable and our failure continues for 90 days and the time for payment has not been extended;



•

if we fail to pay the principal, premium or sinking fund payment, if any, when due and payable at maturity, upon redemption or repurchase or otherwise, and the time for payment has not been extended;



•

if we fail to observe or perform any other covenant contained in the debt securities or the indentures, other than a covenant specifically relating to another series of debt securities, and our failure continues for 90 days after we receive notice from the trustee or holders of at least 25% in aggregate principal amount of the outstanding debt securities of the applicable series; and

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•

if specified events of bankruptcy, insolvency or reorganization occur.

        We will describe in each applicable prospectus supplement or free writing prospectus any additional events of default relating to the relevant series of debt securities.

        If an event of default with respect to debt securities of any series occurs and is continuing, other than an event of default specified in the last bullet point above, the trustee or the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series, by notice to us in writing, and to the trustee if notice is given by such holders, may declare the unpaid principal, premium, if any, and accrued interest, if any, due and payable immediately. If an event of default specified in the last bullet point above occurs with respect to us, the unpaid principal, premium, if any, and accrued interest, if any, of each issue of debt securities then outstanding shall be due and payable without any notice or other action on the part of the trustee or any holder.

        The holders of a majority in principal amount of the outstanding debt securities of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events of default regarding payment of principal, premium, if any, or interest, unless we have cured the default or event of default in accordance with the indenture. Any waiver shall cure the default or event of default.

        Subject to the terms of the indentures, if an event of default under an indenture shall occur and be continuing, the trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of debt securities, unless such holders have offered the trustee reasonable indemnity or security satisfactory to it against any loss, liability or expense. The holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee, or exercising any trust or power conferred on the trustee, with respect to the debt securities of that series, provided that:

•

the direction so given by the holder is not in conflict with any law or the applicable indenture; and



•

subject to its duties under the Trust Indenture Act, the trustee need not take any action that might involve it in personal liability or might be unduly prejudicial to the holders not involved in the proceeding.

        A holder of the debt securities of any series will have the right to institute a proceeding under the indentures or to appoint a receiver or trustee, or to seek other remedies if:

•

the holder has given written notice to the trustee of a continuing event of default with respect to that series;



•

the holders of at least 25% in aggregate principal amount of the outstanding debt securities of that series have made written request, and such holders have offered reasonable indemnity to the trustee or security satisfactory to it against any loss, liability or expense or to be incurred in compliance with instituting the proceeding as trustee; and



•

the trustee does not institute the proceeding, and does not receive from the holders of a majority in aggregate principal amount of the outstanding debt securities of that series other conflicting directions within 90 days after the notice, request and offer.

        These limitations do not apply to a suit instituted by a holder of debt securities if we default in the payment of the principal, premium, if any, or interest on, the debt securities, or other defaults that may be specified in the applicable prospectus supplement or free writing prospectus.

        We will periodically file statements with the trustee regarding our compliance with specified covenants in the indentures.

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Modification of Indenture; Waiver

        Subject to the terms of the indenture for any series of debt securities that we may issue, we and the trustee may change an indenture without the consent of any holders with respect to the following specific matters:

•

to fix any ambiguity, defect or inconsistency in the indenture;



•

to comply with the provisions described above under "Description of Our Debt Securities—Consolidation, Merger or Sale;"



•

to comply with any requirements of the SEC in connection with the qualification of any indenture under the Trust Indenture Act;



•

to add to, delete from or revise the conditions, limitations, and restrictions on the authorized amount, terms, or purposes of issue, authentication and delivery of debt securities, as set forth in the indenture;



•

to provide for the issuance of and establish the form and terms and conditions of the debt securities of any series as provided under "Description of Our Debt Securities—General," to establish the form of any certifications required to be furnished pursuant to the terms of the indenture or any series of debt securities, or to add to the rights of the holders of any series of debt securities;



•

to evidence and provide for the acceptance of appointment hereunder by a successor trustee;



•

to provide for uncertificated debt securities and to make all appropriate changes for such purpose;



•

to add to our covenants such new covenants, restrictions, conditions or provisions for the benefit of the holders, to make the occurrence, or the occurrence and the continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default or to surrender any right or power conferred to us in the indenture; or



•

to change anything that does not materially adversely affect the interests of any holder of debt securities of any series.

        In addition, under the indentures, the rights of holders of a series of debt securities may be changed by us and the trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series that is affected. However, subject to the terms of the indenture for any series of debt securities that we may issue or as otherwise provided in the prospectus supplement or free writing prospectus applicable to a particular series of debt securities, we and the trustee may make the following changes only with the consent of each holder of any outstanding debt securities affected:

•

extending the stated maturity of the series of debt securities;



•

reducing the principal amount, reducing the rate of or extending the time of payment of interest, or reducing any premium payable upon the redemption or repurchase of any debt securities; or



•

reducing the percentage of debt securities, the holders of which are required to consent to any amendment, supplement, modification or waiver.

Discharge

        Each indenture provides that, subject to the terms of the indenture and any limitation otherwise provided in the prospectus supplement or free writing prospectus applicable to a particular series of

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debt securities, we can elect to be discharged from our obligations with respect to one or more series of debt securities, except for specified obligations, including obligations to:

•

register the transfer or exchange of debt securities of the series;



•

replace stolen, lost or mutilated debt securities of the series;



•

maintain paying agencies;



•

hold monies for payment in trust;



•

recover excess money held by the trustee;



•

compensate and indemnify the trustee; and



•

appoint any successor trustee.

        In order to exercise our rights to be discharged, we must deposit with the trustee money or government obligations sufficient to pay all the principal of, any premium and interest on, the debt securities of the series on the dates payments are due.

Form, Exchange and Transfer

        We will issue the debt securities of each series only in fully registered form without coupons and, unless we otherwise specify in the applicable prospectus supplement or free writing prospectus, in denominations of $1,000 and any integral multiple thereof. The indentures provide that we may issue debt securities of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company or another depository named by us and identified in a prospectus supplement or free writing prospectus with respect to that series.

        At the option of the holder, subject to the terms of the indentures and the limitations applicable to global securities described in the applicable prospectus supplement or free writing prospectus, the holder of the debt securities of any series can exchange the debt securities for other debt securities of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

        Subject to the terms of the indentures and the limitations applicable to global securities set forth in the applicable prospectus supplement or free writing prospectus, holders of the debt securities may present the debt securities for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the debt securities that the holder presents for transfer or exchange, we will make no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

        We will name in the applicable prospectus supplement or free writing prospectus the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any debt securities. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the debt securities of each series. If we elect to redeem the debt securities of any series, we will not be required to:

•

issue, register the transfer of, or exchange any debt securities of that series during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption of any debt securities that may be selected for redemption and ending at the close of business on the day of the mailing; or



•

register the transfer of or exchange any debt securities so selected for redemption, in whole or in part, except the unredeemed portion of any debt securities we are redeeming in part.

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Information Concerning the Trustee

        The trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture. Upon an event of default under an indenture, the trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs.

        Subject to this provision, the trustee is under no obligation to exercise any of the powers given it by the indentures at the request of any holder of debt securities unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur.

Payment and Paying Agents

        Unless we otherwise indicate in the applicable prospectus supplement or free writing prospectus, we will make payment of the interest on any debt securities on any interest payment date to the person in whose name the debt securities, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest.

        We will pay principal of and any premium and interest on the debt securities of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement or free writing prospectus, we will make interest payments by check that we will mail to the holder or by wire transfer to certain holders. Unless we otherwise indicate in the applicable prospectus supplement or free writing prospectus, we will designate the corporate trust office of the trustee as our sole paying agent for payments with respect to debt securities of each series. We will name in the applicable prospectus supplement or free writing prospectus any other paying agents that we initially designate for the debt securities of a particular series. We will maintain a paying agent in each place of payment for the debt securities of a particular series.

        All money we pay to a paying agent or the trustee for the payment of the principal of or any premium or interest on any debt securities that remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the debt security thereafter may look only to us for payment thereof.

Governing Law

        The indentures and the debt securities will be governed by and construed in accordance with the laws of the State of New York, except to the extent that the Trust Indenture Act is applicable.

Ranking of Debt Securities

        The subordinated debt securities will be subordinate and junior in priority of payment to certain of our other indebtedness to the extent described in a prospectus supplement or free writing prospectus. The subordinated indenture does not limit the amount of subordinated debt securities that we may issue. It also does not limit us from issuing any other secured or unsecured debt.

        The senior debt securities will rank equally in right of payment to all our other senior unsecured debt. The senior indenture does not limit the amount of senior debt securities that we may issue. It also does not limit us from issuing any other secured or unsecured debt.

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DESCRIPTION OF UNITS

        We may issue units comprised of shares of common stock, shares of preferred stock, debt securities and warrants in any combination. We may issue units in such amounts and in as many distinct series as we wish. This section outlines certain provisions of the units that we may issue. If we issue units, they will be issued under one or more unit agreements to be entered into between us and a bank or other financial institution, as unit agent. The specific terms of any series of units offered will be described in the applicable prospectus supplement or free writing prospectus. The specific terms of any series of units may differ from the general description of terms presented below.

        We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of unit agreement that describes the terms of the series of units we are offering, and any supplemental agreements, before the issuance of the related series of units. The following summaries of material terms and provisions of the units are subject to, and qualified in their entirety by reference to, all the provisions of the unit agreement and any supplemental agreements applicable to a particular series of units. We urge you to read any prospectus supplement related to any series of units we may offer, as well as the complete unit agreement and unit certificate that contain the terms of the units.

General

        Each unit that we may issue will be issued so that the holder of the unit is also the holder of each security included in the unit. Thus, the holder of a unit will have the rights and obligations of a holder of each included security. The unit agreement under which a unit is issued may provide that the securities included in the unit may not be held or transferred separately, at any time or at any time before a specified date. The applicable prospectus supplement may describe:

•

the designation and terms of the units and of the securities comprising the units, including whether and under what circumstances those securities may be held or transferred separately;



•

any provisions of the governing unit agreement;



•

the price or prices at which such units will be issued;



•

the applicable United States federal income tax considerations relating to the units;



•

any provisions for the issuance, payment, settlement, transfer or exchange of the units or of the securities comprising the units; and



•

any other terms of the units and of the securities comprising the units.

        The provisions described in this section, as well as those described under "Description of Common Stock and Preferred Stock," "Description of Warrants" and "Description of Debt Securities" will apply to the securities included in each unit, to the extent relevant and as may be updated in any prospectus supplements.

Issuance in Series

        We may issue units in such amounts and in as many distinct series as we wish. This section summarizes terms of the units that apply generally to all series. Most of the financial and other specific terms of a particular series of units will be described in the applicable prospectus supplement.

Unit Agreements

        We will issue the units under one or more unit agreements to be entered into between us and a bank or other financial institution, as unit agent. We may add, replace or terminate unit agents from

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time to time. We will identify the unit agreement under which each series of units will be issued and the unit agent under that agreement in the applicable prospectus supplement.

        The following provisions will generally apply to all unit agreements unless otherwise stated in the applicable prospectus supplement:

Modification without Consent

        We and the applicable unit agent may amend any unit or unit agreement without the consent of any holder:

•

to cure any ambiguity, including modifying any provisions of the governing unit agreement that differ from those described below;



•

to correct or supplement any defective or inconsistent provision; or



•

to make any other change that we believe is necessary or desirable and will not adversely affect the interests of the affected holders in any material respect.