The Greeks are the four forces that control options pricing beyond the stock price itself. If you're trading options without understanding the Greeks, you're driving blindfolded. Delta measures how much an option's price moves per $1 change in the stock. A call with 0.50 delta moves $0.50 for every $1 the stock moves. Deep in-the-money options have deltas near 1.0 (they move almost dollar-for-dollar with the stock). Out-of-the-money options have small deltas. Delta also approximates the probability of expiring in-the-money.

Gamma is the rate of change of delta — it tells you how fast delta itself is changing. Gamma is highest for at-the-money options near expiration. This is where options become most dangerous and most profitable. A high-gamma option can see its delta swing wildly as the stock moves back and forth across the strike price. This is called 'gamma risk' and it's why market makers actively hedge their gamma exposure. Gamma is the reason options near expiration can produce 100%+ moves in a single day.

Theta is time decay — the amount of value an option loses each day just from time passing. Options are wasting assets; they lose value every single day as expiration approaches. Theta accelerates dramatically in the final 30 days. If you're buying options, theta is your enemy. If you're selling options, theta is your friend. The 'theta gang' strategy involves selling options to collect premium and profiting from time decay. Understanding theta helps you choose the right expiration date — too short and theta will eat your position, too long and you're overpaying for time value.

Vega measures sensitivity to implied volatility changes. When IV increases, all options become more expensive (higher premiums). When IV decreases, options become cheaper. This is why buying options before earnings (when IV is high) can be a losing trade even if you're right about direction — the post-earnings IV crush can destroy your option's value. Vega is highest for at-the-money options with longer expirations. Understanding vega helps you time option purchases around volatility events and avoid paying too much when IV is elevated.