- Delta: how much the option price changes for a 1-point move in the underlying. A 0.5 delta call gains about ₹0.50 when NIFTY rises 1 point. Calls have positive delta, puts negative.
- Gamma: how fast delta changes. It is highest for at-the-money options near expiry, which is why their prices can jump suddenly.
- Theta: the value an option loses per day if nothing else changes. Buyers pay theta; sellers earn it.
- Vega: how much the option price changes when implied volatility moves by 1 percentage point.
For a whole strategy
Add up the Greeks of every leg (times lots and lot size). A short straddle, for example, has near-zero delta, negative gamma, positive theta and negative vega: it earns from time passing and loses on big moves or rising IV.