Definition of Delta
The ratio of the change in price of an option to the change in price of the underlying asset. Also called the hedge ratio. Applies to derivative products. For a call option on a stock, a delta of 0.50 means that for every $1.00 that the stock goes up, the option price rises by $0.50. As options near expiration, in-the-money call option contracts approach a delta of 1.0, while in-the-money put options approach a delta of -1. See: hedge ratio, neutral hedge. Call deltas range from 0.00 to +1.00; put deltas range from 0.00 to -1.00. If the call delta is 0.69, the put delta is -0.31 (call delta minus 1 equals put delta; 0.69 -1 =-0.31).