The Greeks, in the order they matter

5 min read•Updated on 6 Sep 2026•by GeniAnalysis

Delta, gamma, theta and vega, what each separates out, and how they interact.

An option's price moves for several reasons at once. The underlying moves. Time passes. Expectations about volatility change.

On any given day all three are happening together, which is why an option can behave in ways that seem to contradict a correct read on direction. The Greeks exist to separate those reasons, so that a price move can be attributed rather than guessed at.

There are five in common use. Two of them carry most of the weight.

Delta

Delta measures how much the option's price moves for a one-point move in the underlying.

A call with a delta of 0.45 gains roughly 45 paise for every rupee the underlying rises, and loses the same on the way down. Calls have positive delta, puts negative. Deep in-the-money options approach a delta of 1, meaning they track the underlying almost point for point. Far out-of-the-money options approach zero and barely respond at all.

Delta is also commonly read as a rough approximation of the chance the option finishes in the money. A 0.30 delta call is loosely treated as having about a 30 per cent chance of expiring with value. This is a useful mental shortcut and it is not a probability. It comes out of the pricing model's assumptions, not out of any observation of how often such options actually finish in the money.

Gamma

Gamma measures how fast delta itself changes as the underlying moves.

If delta is speed, gamma is acceleration. A position with high gamma sees its delta shift quickly, which means its exposure to the underlying is not stable. A position with low gamma behaves predictably.

Gamma is highest for at-the-money options and rises sharply as expiry approaches. That combination is why short-dated at-the-money options behave the way they do: a modest move in the underlying can take an option from barely responsive to nearly one-for-one within a session. The position you are holding at 2pm is not the position you opened at 10am, even though nothing about the contract changed.

This is the Greek that explains why weekly options feel unstable. It is not sentiment. It is gamma.

Theta

Theta measures the value lost to the passage of time, usually expressed per day.

Every option loses value as expiry approaches, all else equal, because there is less time remaining for the underlying to move. Theta is that decay.

Two things about it are commonly misunderstood.

It is not linear. Decay accelerates as expiry nears, and the final days of a series remove value far faster than the first days. An option that lost a little each day for three weeks can lose a large fraction of what is left in the last two sessions.

And it is largest for at-the-money options. Deep in-the-money options are mostly intrinsic value, which does not decay. Far out-of-the-money options have little left to lose. The money is in the middle, and so is the decay.

Vega

Vega measures sensitivity to implied volatility. How much the option's price changes when IV moves by one percentage point.

This is the Greek that catches people out, so it is worth being direct about the mechanism.

You can be right about direction and still lose money.

Buy a call ahead of a result because you expect the stock to rise. IV is elevated going in, because the market is pricing uncertainty around the announcement. The result lands, the stock rises as you expected, and IV collapses because the uncertainty is now resolved. The gain from the move and the loss from the volatility drop can offset, and sometimes the second is larger.

Nothing went wrong with the directional call. The position simply had exposure to something other than direction, and that something moved against it. Vega is the number that would have shown this before the trade rather than after.

Vega is highest for at-the-money options and for options with more time to expiry. Long-dated options carry far more volatility exposure than weekly ones.

Rho

Rho measures sensitivity to interest rates.

For short-dated Indian F&O it rarely matters enough to think about. It is worth knowing the term exists and worth not spending time on it unless you are dealing in long-dated positions.

How they interact

The Greeks are not independent readings to be checked in turn. They describe one position from different angles, and they pull against each other.

The clearest tension is between gamma and theta. An at-the-money option close to expiry has high gamma, meaning it responds sharply to movement. It also has high theta, meaning it bleeds value quickly if nothing happens. Those are two sides of the same position. You cannot hold the responsiveness without also holding the decay, and a position taken for one is exposed to the other whether or not you were thinking about it.

Vega runs the other way on time. Short-dated options carry little volatility exposure and heavy decay. Long-dated options carry heavy volatility exposure and gentle decay.

Every option position is therefore a specific combination of these exposures, decided largely by the strike and the expiry chosen. Choosing those two things is choosing the Greeks, whether or not the choice was made deliberately.

Reading them on the chain

The practical version of all of this is looking at the Greeks per strike rather than in the abstract.

Comparing delta across strikes shows how exposure changes as you move away from the money. Comparing theta shows what each choice costs per day. Comparing vega shows which strikes carry the volatility exposure. Those comparisons make the trade-offs concrete in a way that definitions do not.

A worked example

The same call option, looked at three times.

Twenty days to expiry, underlying at 1,000, strike 1,020. Delta 0.38, gamma low, theta small, vega meaningful. The position responds moderately to movement, loses little to each passing day, and carries real exposure to any change in implied volatility.

Five days to expiry, underlying still at 1,000. Delta has fallen, because with less time remaining the option is less likely to get there. Gamma has risen sharply. Theta has roughly tripled. Vega has fallen away. The underlying has not moved at all, and the position has changed character completely.

Two days to expiry, underlying at 1,018. Delta is now near 0.5 and moving fast on every tick. A one per cent move in either direction swings the position's exposure dramatically. Theta is removing a large share of the remaining premium each day.

Across all three snapshots, one directional view was held throughout. What changed was everything about how the position expressed it. Reading the Greeks is what makes that visible before it happens rather than afterwards.

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