Understanding Option Greeks — Delta, Gamma, Vega, and Theta (Simplified with Correct Visuals)
In options trading, Greeks are vital for understanding how option prices react to market changes. Each Greek — Delta, Gamma, Vega, and Theta — measures a specific sensitivity, helping traders manage risk and anticipate moves.
📊 Summary Table
| Greek | What It Measures | Example | Effect |
|---|---|---|---|
| Delta | Change in option price for $1 change in stock | Stock +$1, Delta = 0.5 → Option +$0.50 | Price sensitivity to stock move |
| Gamma | Change in Delta per $1 stock move | Gamma = 0.05 → Delta 0.5 → 0.55 | Acceleration of Delta |
| Vega | Change in option price for 1% volatility change | Vol ↑1% → Option +$0.10 | Volatility sensitivity |
| Theta | Change in option price per day | Theta = -0.05 → Option loses $0.05/day | Time decay |
🔹 1. Delta — Option’s Reaction to Stock Price Movement
Delta shows how much the option price moves when the stock moves $1. Calls have positive Delta (0 to 1), puts have negative (-1 to 0).
Delta increases as the stock price rises for call options. At-the-money options have Delta ≈ 0.5, deep in-the-money ≈ 1.
🔹 2. Gamma — How Fast Delta Changes
Gamma measures the *curvature* of Delta — how quickly Delta changes when the stock moves. It’s highest when the option is near-the-money.
Gamma peaks when the option is near-the-money. This means Delta changes fastest around that point — giving options strong responsiveness to price movement.
🔹 3. Vega — Sensitivity to Volatility
Vega measures how much an option’s price changes with a 1% change in implied volatility. Both calls and puts gain value when volatility rises.
Vega is highest for near-the-money options and declines for deep ITM or OTM ones. A Vega of 0.10 means the option gains $0.10 if volatility increases by 1%.
🔹 4. Theta — Time Decay
Theta measures how much an option loses value each day as expiration approaches. This is known as time decay.
Theta is always negative for long options. As expiry nears, time decay accelerates — options lose value faster even if the stock doesn’t move.
✅ Quick Recap
- Delta → Directional sensitivity (linear curve upward).
- Gamma → How fast Delta changes (bell-shaped curve).
- Vega → Sensitivity to volatility (broad bell curve).
- Theta → Time decay (downward sloping curve).
By combining these Greeks, traders can forecast how an option will behave under different scenarios — helping in strategy selection, hedging, and timing.
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