Greeks

The group of five main measurements of the sensitivity of the value of an option to various key factors, often represented by a Greek letter: delta or δ measuring sensitivity to changes in the price of the underlying, gamma or γ measuring sensitivity of the delta to changes in the price of the underlying, theta or θ measuring sensitivity to time decay, rho or ρ measuring sensitivity to interest rate fluctuations, and vega measuring sensitivity to the volatility of the underlying (while vega is not the name of a Greek letter, it is sometimes represented by the Greek letter nu or v).