The Greeks are a set of risk measures, each named after a Greek letter, that describe how an option's price changes as different inputs move. Ignoring them means trading a position without knowing what it's actually exposed to.
Delta: Directional Exposure
Delta measures how much an option's price moves for a $1 move in the underlying, and ranges from 0 to 1 for calls (0 to −1 for puts). A 0.50 delta call gains roughly $0.50 for every $1 the stock rises. Delta also approximates the probability the option finishes in the money.
| Position | Delta Sign |
|---|---|
| Long call | Positive (0 to +1) |
| Short call | Negative (0 to −1) |
| Long put | Negative (0 to −1) |
| Short put | Positive (0 to +1) |
Gamma: The Rate of Change of Delta
Gamma tells you how fast delta itself changes as the underlying moves. Gamma is highest for at-the-money options near expiry, which is exactly why 0DTE options can whipsaw a position's exposure so violently — delta can swing from 0.20 to 0.80 within minutes on a sharp move.
Theta: Time Decay
Theta is expressed as a negative number for long options, representing the dollar amount of premium lost per day, all else equal. A theta of −0.08 on a $3.00 option means it loses roughly $8 per contract per day just from time passing.
Theta ≈ Change in option price per day, holding spot and IV constantVega: Volatility Sensitivity
Vega measures the dollar change in premium for a 1-percentage-point change in implied volatility. A long option always has positive vega — it benefits from rising IV — while a short option has negative vega and profits when IV falls.
Rho: Interest Rate Sensitivity
Rho measures sensitivity to interest rate changes. It's the least important Greek for short-dated options but matters more for LEAPS (long-dated options), where rate changes over a year or more can meaningfully shift pricing.
A long call at 0.40 delta, 0.05 gamma, −0.06 theta, and 0.10 vega tells a story: moderately bullish exposure, accelerating gains if the stock rallies, a $6/day decay cost, and a $10 gain per 1-point rise in IV. Reading the Greeks together, not individually, is what real risk management looks like.
Every options position, no matter how complex, can be reduced to a net delta, gamma, theta, and vega. Professional desks manage entire portfolios by keeping these aggregate exposures within limits — the same discipline scales down perfectly to a single retail account.