Gamma - Definition
Gamma is the amount by which an option’s delta value will change with a corresponding change in price by the underlying stock.


Gamma Explained
Very simply put, Gamma is an Options Greek that determines how much Options Delta changes with a $1 change in the price of the underlying stock. Positive Gamma makes delta more and more positive when the underlying stock rises while a negative gamma makes delta more and more negative when the underlying stock rises. All long stock options have positive gamma while all short stock options have negative gamma no matter they be Call Options or Put Options.