Here’s a summary of the so-called option “greeks”. These definitions are mostly (loosely) edited versions of definitions provided by Investopedia.com:
1. Theta is a measure of the rate of change in the value of an option due to the passage of time. Other things equal, the call option loses value as time moves closer to the maturity/expiration date. On the other hand, deeply in-the-money put options increase in value as time moves closer to the maturity/expiration date, although puts that aren’t deeply in-the-money decline in value.
2. Delta is the ratio comparing the change in the price of the underlying asset to the corresponding change in the price of an option. For example, if an option has a delta value of 0.65, this means that if the underlying stock increases in price by $1, the option will rise by approximately $0.65, other things equal.
3. Gamma is the rate of change in an option’s delta per $1 change in the underlying asset’s price. Gamma is an important measure of the convexity of an option’s value, in relation to the underlying. Gamma has a low value (near zero) for options that are deeply in or out-of-the-money, but have much higher value when they trade at-the-money.
4. Rho is the rate at which the price of an option changes relative to a change in the risk-free rate of interest. Rho is positive for call options, and negative for put options. Rho measures the sensitivity of the price of an option to a change in interest rate. For example, if rho = 50, this means that if the interest rate increases (decreases) by 1%, the price of a call option increases (decreases) by approximately 50 cents
5. Vega is the measurement of an option’s sensitivity to changes in the volatility of the underlying asset. Vega represents the amount that an option contract’s price changes in reaction to a 1% change in the volatility of the underlying asset. Vega is positive for calls and puts alike.