DEFINITION of 'Delta'
The ratio comparing the change in the price of the underlying asset to the corresponding change in the price of a derivative. Sometimes referred to as the "hedge ratio."
INVESTOPEDIA EXPLAINS 'Delta'
For example, with respect to call options, a delta of 0.7 means that for every $1 the underlying stock increases, the call option will increase by $0.70.
Put option deltas, on the other hand, will be negative, because as the underlying security increases, the value of the option will decrease. So a put option with a delta of 0.7 will decrease by $0.70 for every $1 the underlying increases in price.
As an inthemoney call option nears expiration, it will approach a delta of 1.00, and as an inthemoney put option nears expiration, it will approach a delta of 1.00.
RELATED TERMS

Zomma
An options greek used to measure the change in gamma in relation ... 
Delta Spread
An options trading strategy where the trader initially establishes ... 
Call Option
An agreement that gives an investor the right (but not the obligation) ... 
Expiration Date
The last day that an options or futures contract is valid. When ... 
Gamma
The rate of change for delta with respect to the underlying asset's ... 
Greeks
Dimensions of risk involved in taking a position in an option ...
Related Articles

Options & Futures
Reducing Risk With Options

Options & Futures
The Basics Of Option Price

Options & Futures
An Introduction To GammaDelta Neutral ...

Options & Futures
Getting To Know The "Greeks"