"The Greeks" that investors often talk about are the different ways risks can be measured for any particular stock or option.**Option Delta** - The delta of an option is how much the value of the option will go up if the underlying stock goes up one dollar.**Option Theta** - Theta is the measure of daily "decay" of an option's value, which is the amount the option will fall in value given a flat trading day for the stock.**Option Gamma **- Gamma is the amount the delta will change if the underlying stock goes up one dollar.