New video in the series on learning options with AI, leaning on ChatGPT as if we knew nothing about options. We’ve already covered the Call, the Put, moneyness and implied volatility. Today we get into the core of options trading: the Greeks. Delta, gamma, theta and vega — what separates someone who buys options from someone who actually understands how they work.
What the Greeks are
The Greeks are measures that show how an option’s price will change when one of the factors affecting it changes. They’re not something made up — they’re a calculation method to know how that price is going to move.
Imagine an option is a car. Its price depends on four “pedals”: the stock price, the passage of time, volatility, and how fast all of the above changes. The Greeks tell us how the car reacts when we press each pedal.
Delta: the most important Greek
Delta shows how much an option’s price changes when the stock moves $1 up or down. It’s the most important Greek and one of the ones most worth keeping an eye on.
Example: Apple trades at $100 and we buy a call worth $4 with a delta of 0.50. If Apple goes from $100 to $101, the option should rise about $0.50, going from $4 to $4.50. And the reverse: if Apple drops $1, the option drops $0.50.
With Apple at $100, an 80-strike call is deep in the money, the 100-strike is at the money, and the 120-strike is way out of the money. Which one reacts more if Apple rises $1? The 80-strike, because it already has a lot of intrinsic value — the deeper ITM an option is, the more it’s affected by the stock’s move. Calls have positive delta and puts have negative delta (that’s basically their only quirk, since they’re the mirror image of each other).
A very useful trick: many traders use delta as a rough approximation of the probability of expiring in the money. A delta of 0.80 roughly means an ~80% probability; a 0.30, roughly ~30%. It’s not an exact rule — take it with a grain of salt — but it’s a widely used reference. We also touched on this in the article about how to choose the strike and expiration.
Gamma: the acceleration of delta
Delta isn’t fixed — it keeps changing continuously. And what makes it change is gamma. Example: a call with an initial delta of 0.40; if Apple rises several dollars and gets closer to being in the money, its delta moves to 0.55, then 0.68, then 0.82. That acceleration is exactly what gamma measures.
Following the car analogy: delta is speed, and gamma is acceleration — how fast you reach your desired speed. It’s not the same to cruise steadily at 60 mph as it is to go from 30 to 60 in two seconds.
Gamma is highest when an option is at the money and very close to expiration. That’s why options near expiration can swing in price very violently: any small move in the underlying massively accelerates the option’s value. You can build intraday strategies around this, but the odds are usually stacked against you.
Theta: the passage of time
Theta measures how much an option loses simply because a day goes by. And there’s a fundamental asymmetry here:
- If you’re long an option, theta works against you: every day that passes, it loses a bit of value
- If you’re a seller of options, theta works in your favor: every day that passes without big moves, you profit simply from the passage of time
Time favors the option seller — as long as the underlying doesn’t do anything crazy. Sometimes all you have to do is let time pass.
Vega: sensitivity to volatility
Vega measures how much an option’s price changes when implied volatility changes. And implied volatility is present in everything surrounding options. Example: you buy a call with a vega of 0.25; if implied volatility goes from 20% to 21%, the option gains about $0.25 even if the stock hasn’t moved at all.
If implied volatility drops, the option loses value. That’s why the famous IV crash happens after earnings are released: before the event, volatility rises (there’s uncertainty, more people want to hedge, so demand and premiums go up); once the event passes and things calm down, that volatility disappears and options go back to “normal” prices. You have this in detail in the article on earnings and the IV crash.
Seeing it on ProRealTime
As always in this series, after the theory we move to a professional platform to see where these Greeks actually are with real data. In ProRealTime‘s option chain, you can see the delta, gamma, theta and vega of every contract, and watch live how they move as price, time or volatility change.
Conclusion
The Greeks are the calculation method that tells you how an option’s price is going to react to each factor: delta (the price move), gamma (the acceleration of delta), theta (the passage of time), and vega (volatility). With the car analogy — price, time, volatility, and the speed at which they change — it all clicks much better. Understanding the Greeks is exactly what separates someone who buys options from someone who truly understands what they’re holding. Don’t forget to comment and like to keep following the series.
