Educational only. This explains how option Greeks work. It is not a recommendation to buy, sell, or trade any instrument, and it makes no prediction about any market or price. TradeDNA is a post-trade analytics journal, not an investment adviser.
If you trade options on NSE and the words delta, theta or IV still feel fuzzy, this is for you. The Greeks aren't academic — they're the reason an option can move against you even when the underlying goes your way. Here's each one, in plain English.
Delta — how much the option moves with the underlying
Delta measures how much an option's price changes for a ₹1 move in the underlying.
- A call with a delta of 0.5 gains roughly ₹0.50 for every ₹1 the underlying rises.
- Calls have deltas from 0 to 1; puts from 0 to −1.
- Deep in-the-money options have deltas near ±1 (they move almost like the stock/future). Far out-of-the-money options have deltas near 0 (they barely respond).
Delta is also a rough proxy for the probability the option finishes in-the-money. An ATM option sits near 0.5 — a coin flip.
Gamma — how fast delta itself changes
Gamma measures how much delta changes for a ₹1 move in the underlying. It's the "acceleration" behind delta's "speed."
- Gamma is highest for at-the-money options near expiry. That's why ATM options on expiry day can swing wildly — a small move in the underlying flips delta fast.
- High gamma cuts both ways: your position can gain (or lose) far quicker than the raw delta suggests.
If you've ever watched an expiry-day ATM option double and then go to zero within minutes, you've watched gamma at work.
Theta — the clock ticking against option buyers
Theta measures how much value an option loses per day, purely from time passing — assuming nothing else changes. This is time decay.
- Theta is negative for buyers (you lose a little every day) and positive for sellers (they collect it).
- Decay is not linear — it accelerates as expiry approaches, and it's fastest for at-the-money options in the final days.
- This is why so many option buyers lose even when they get the direction roughly right: they were correct, but too slow, and theta bled the premium away while they waited.
Theta is the single most under-appreciated Greek for retail buyers. If you routinely buy weekly options and hold them, decay is a headwind you're paying every single day.
Vega — sensitivity to volatility
Vega measures how much an option's price changes for a 1-point move in implied volatility (IV).
- Higher IV = more expensive options (bigger expected swings priced in). Lower IV = cheaper options.
- Buyers are long vega — they benefit when IV rises. Sellers are short vega.
- IV crush is the classic trap: you buy options before a known event (results, a policy day) when IV is inflated, the event passes, IV collapses, and your option loses value even if the underlying moved your way. The direction was right; vega killed the trade.
Rho — sensitivity to interest rates
Rho measures sensitivity to interest-rate changes. For short-dated Indian index and stock options, rho is small enough that most intraday and weekly traders can safely ignore it. It matters more for long-dated options.
How the Greeks work together near expiry
The Greeks aren't independent — near expiry they gang up:
- Gamma spikes, so delta becomes twitchy.
- Theta accelerates, so time decay is brutal on any option that isn't moving.
- Vega shrinks (less time = less volatility value), so IV matters less as expiry nears.
That combination is why expiry day feels chaotic: tiny moves cause big percentage swings (gamma), and anything not moving is bleeding fast (theta).
The behavioural angle — where most retail money actually goes
Understanding the Greeks is necessary, but it's not where most retail F&O accounts bleed. The bigger leaks are behavioural — and they interact with the Greeks:
- Holding losing option buys "to recover" — while theta decays the premium every day you wait.
- Buying options into events at inflated IV — then getting IV-crushed.
- Over-trading weekly expiries — where theta and gamma are at their most punishing, and charges pile up on every square-off.
You can't see those patterns in a single trade. You see them across dozens — which is exactly what a post-trade journal is for. TradeDNA reads your own tradebook and surfaces the repeating habits — overtrading, revenge trades, holding losers — that quietly drain the account, retrospectively and in plain English.
See the patterns in your own trades — free, no signup.
This article is educational. It does not recommend any trade, instrument, or strategy, and makes no forecast. Verify all rules and rates against official NSE/SEBI sources.