Delta measures the sensitivity of an option relative to the underlying asset. It measures the rate of change in the price of an option with respect to a price change in the underlying asset. Delta tells an investor about the relationship between a change in the option price with respect to a change in its underlying asset price. For example, an option with a delta of 0.9 moves 90 cents for every $1 move in the underlying stock.
The value of delta is affected by time decay and implied volatility. As the time to expiration of an option decreases, the delta of outofthemoney options decreases, while the delta of inthemoney options increases. As implied volatility rises, investors believe the underlying asset price will have a greater change in price, which will change the value of delta. Generally, an increase in implied volatility causes delta to move toward 0.5, which means an option moves 50 cents for every $1 move in the underlying asset.
As a call option gets deep in the money and closer to expiration, the value of delta gets closer to 1. As a put option gets deeper in the money and closer to expiration, the value of delta gets closer to 1.
A long stock position has a delta of 1, while a short stock position has a delta of 1. Since the delta of a long stock position is bounded by 0 and 1, an option cannot exceed that value. On the other hand, the delta of a short stock position is bounded by 0 and 1, so an option cannot be lower than that value.

How can I calculate the delta adjusted notional value?
Find out how to calculate the delta adjusted notional value of an options contract, and why gross notional value cannot be ... Read Answer >> 
Can delta be used to calculate price volatility of an option?
Learn how implied volatility is an output of the BlackScholes option pricing formula, and learn about that option formula's ... Read Answer >> 
Do options make more sense during bull or bear markets?
Understand how options may be used in both bullish and bearish markets, and learn the basics of options pricing and certain ... Read Answer >>

Trading
Options Trading Strategies: Understanding Position Delta
Learn more about the position delta hedge ratio and how it can tell you the number of contracts needed to hedge a position in the underlying asset. 
Retirement
Is Delta Stock Suitable for Your IRA or Roth IRA? (DAL)
Learn about Delta Airlines and the factors that affect the company's performance. Discover if Delta stock makes an appropriate investment for IRA accounts. 
Trading
Getting To Know The "Greeks"
Understanding price influences on options positions requires learning about delta, theta, vega and gamma. 
Insights
Delta Releases Q4 & 2016 Revenue Figures (DAL)
Delta’s revenue figures for Q4 and 2016 are down from the previous year, mostly due to declines in passenger revenue. 
Investing
Delta Air Line's Potential Pitfalls (DAL)
During Delta Airline's (NYSE: DAL) fourthquarter 2014 earnings call in late January, CEO Richard Anderson rattled off the following impressive statistics about the company and its stock: We ... 
Investing
Delta's 3 Key Financial Ratios (DAL)
Learn why a smaller sales growth rate is actually good for an airline company such as Delta to achieve a better operating margin and higher stock valuation.

Delta Neutral
Delta neutral is a portfolio strategy consisting of positions ... 
Delta
Delta is the ratio comparing the change in the price of the underlying ... 
Futures Equivalent
The number of futures contracts needed to be associated with ... 
Charm
The rate at which the delta of an option or warrant will change ... 
DeltaGamma Hedging
An options hedging strategy that combines a delta hedge and a ... 
Gamma Hedging
Gamma hedging is an options hedging strategy designed to reduce, ...