Gamma

How fast delta changes as the stock moves.

Why it matters

High gamma means your exposure changes quickly. It is largest at the money and near expiration, which is why sellers close early.

Long options have positive gamma (good on big moves); short options negative gamma.

In the Cluenex app, this explanation opens next to every gamma figure, with the live reading for the stock you are looking at. Open it in Cluenex