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Option Greeks
The Greeks are a set of measures describing how an option's theoretical value responds to changes in different variables. The five Greeks most traders encounter are Delta for the underlying price, Gamma for changes in Delta as the underlying moves, Theta for the passage of time, Vega for implied volatility and Rho for interest rates.
Why it matters to you
An option is affected by several variables simultaneously. The Greeks help separate those risks so traders can better understand why an option may gain or lose value. They are sensitivities, not guaranteed predictions of future PnL.