Vega

Vega is one of the options Greeks — it measures how much an option's price is expected to change for a shift in implied volatility, quoted per one percentage point of IV. An option with a vega of 0.12 would be expected to gain roughly $0.12 in price if implied volatility rose by one point, even if the stock price didn't move at all. Vega tends to be highest for at-the-money options with more time until expiration, and it's the mechanism behind moves like "IV crush" — the sharp drop in an option's price that can follow a known event (like earnings) once the uncertainty resolves and implied volatility collapses. Vega describes a source of risk and price movement that has nothing to do with the stock's direction: a stock that doesn't move at all can still produce a gain or loss in an option's price purely from implied volatility rising or falling.