The Greeks: delta, theta, vega
1In one sentence
The Greeks tell you what moves an option's price: delta (the stock moving), theta (time passing) and vega (volatility changing).
A call can lose money even when the stock goes up, if time and volatility take away more than the move adds. The Greeks show that tug-of-war.
2Try it: change one thing at a time
Example: NVDA is $215. A $220 call with 30 days left, at 40% implied volatility. Pick what happens next.
Prices from the Black-Scholes model with example numbers. Real prices also depend on supply and demand.
33 words to know
Deltaper $1
How much the option's price moves when the stock moves $1. A delta of 0.45 means about $0.45 a share, or $45 a contract.
Thetaper day
How much value the option loses each day from time passing alone. It speeds up near expiration.
Vegaper 1 pt of IV
How much the price changes when implied volatility moves 1 point. Long-dated options have the most vega.
4Watch out
- Delta isn't fixed. It grows as a call moves into the money and shrinks as it moves away. That change is called gamma.
- Theta speeds up. An option loses time value slowly at first and fastest in its last few weeks.
- Vega can beat delta. If volatility falls hard, an option can lose value even when the stock moves the right way.
5Quick check · 3 questions · optional
Now try it for real
See what the Co-Pilot says today about NVDA, TSLA and 8 more stocks, then drag the dot on a real price.
Common questions
What are the option Greeks?
Measures of how an option's price reacts to changes: delta to the stock price, theta to time passing, vega to implied volatility, and gamma to how fast delta itself changes.
What is delta in options?
How much an option's price moves for a $1 move in the stock. Calls have positive delta (0 to 1), puts negative (0 to −1). Delta near 0.5 means the option is near the money.
What is theta decay?
The value an option loses each day as expiration gets closer, assuming nothing else changes. It's small far from expiration and largest in the final weeks.
Education only. Examples use illustrative numbers. Not financial advice; you make your own decisions.