what are option greeks

The greeks are the sensitivities of an option’s price to the different forces acting on it: delta to the underlying’s move, gamma to the rate that delta itself changes, theta to the passage of time, and vega to changes in volatility. Each isolates one reason a premium moves, so together they explain why an option can lose value even when the stock moves your way. They are the vocabulary of managing an option rather than merely buying one.

what is delta in options

Delta is how much an option’s price changes for a one-rupee move in the underlying. A delta of 0.5 means the option gains about ₹0.50 for every ₹1 the stock rises. Delta also approximates the probability the option finishes in the money and tells you the equivalent stock position the option currently behaves like, which is why it is the first greek most traders learn.

what is theta in options

Theta is the rate at which an option loses value simply from time passing, holding everything else constant — the daily cost of time decay. It is negative for an option buyer, who loses a little each day, and positive for the seller, who collects it. Theta accelerates as expiry approaches, which is why out-of-the-money options bleed value fastest in their final days.

why did my option lose money when the stock went up

Usually because another greek moved against you by more than delta helped. If the stock rose only slightly while a day passed, theta’s time decay can outweigh the small delta gain; and if volatility fell at the same time, vega can subtract more still. An option’s price answers to the underlying, time and volatility together, so a favourable move on one can be swamped by the other two.

what is the difference between delta and gamma

Delta measures how much the option price moves when the underlying moves; gamma measures how much delta itself changes as the underlying moves. Delta is the speed, gamma is the acceleration. Gamma is highest for at-the-money options near expiry, which is exactly when an option’s behaviour changes fastest and positions can turn quickly.

The option greeks: delta, gamma, theta, vega

The reason beginners lose money on options they got directionally right is that they think an option has one price driver — the stock. It has at least four, pulling at once. The greeks are simply the names for those four forces. You do not need the mathematics that produces them to use them; you need to know which force is helping you and which is quietly draining the position.

Think of it like this

Speed, brake, ghadi aur mausam

Driving to a destination, four things decide your progress: your speed, how hard you are accelerating or braking, the clock running down on your deadline, and the weather changing around you. Focus only on speed and the deadline or a storm can still defeat you.

In the market

Delta is your speed toward the strike, gamma is your acceleration, theta is the clock running down, and vega is the weather — volatility — shifting. An option buyer who watches only delta is the driver ignoring the clock and the storm.

The four forces, one at a time

Greek	Measures the price’s sensitivity to	For an option buyer
Delta	A move in the underlying	Helps when the move goes your way
Gamma	The rate delta itself changes	Helps buyers near the money; makes moves accelerate
Theta	The passage of time	Works against you — value bleeds daily
Vega	A change in volatility	Helps if volatility rises, hurts if it falls

Delta: speed, and a probability in disguise

Worked example

What a 0.4 delta actually tells you

A call option with delta 0.40

Underlying rises ₹100.40 × ₹10Option gains ≈ ₹4

Equivalent stock positionThe option behaves like 0.4 of the stock≈ 40 shares per contract-unit

Rough probability in-the-moneyDelta approximates this≈ 40%

As the stock rises toward the strikeThis change is gammaDelta rises toward 1

Delta is three things at once: the price sensitivity, the equivalent stock exposure, and a rough probability of finishing in the money. A far out-of-the-money option has a low delta because it is both insensitive to small moves and unlikely to pay off — which is why it looks cheap and so often expires worthless.

Theta: the tax on time

Every day that passes, an option is worth slightly less, because there is less time for the underlying to move in your favour. That is theta, and it is relentless — it applies on weekends too. Theta accelerates as expiry nears, so the cheap, far out-of-the-money options that attract beginners in the last week are precisely the ones decaying fastest. The option seller on the other side is collecting that decay as their edge.

Gamma and vega: acceleration and weather

Gamma is the rate delta changes, and it is largest for at-the-money options close to expiry. High gamma means a position’s exposure shifts fast as the underlying moves — a comfort when you are on the right side and a trap when you are not, because losses accelerate too. Vega measures sensitivity to volatility itself: buy an option and you are long volatility, so a fall in implied volatility subtracts value even if the stock stands still. The next lesson is entirely about that force, because it surprises people most.

Check yourself

You buy a call. The next day the stock is up slightly, but your option is worth less. Which combination best explains it?

What to remember

An option’s price moves for four reasons at once; the greeks name each — delta, gamma, theta, vega.
Delta is price sensitivity, equivalent stock exposure and a rough probability of finishing in the money.
Theta is relentless daily time decay that accelerates near expiry — the seller’s edge, the buyer’s cost.
Gamma is the acceleration of delta; vega is sensitivity to volatility, and buyers are long volatility.
The cheap far-OTM weekly option has three greeks against it — which is why most F&O buyers lose.

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Common questions

Short, direct answers to what people ask about this topic.

what are option greeks: The greeks are the sensitivities of an option’s price to the different forces acting on it: delta to the underlying’s move, gamma to the rate that delta itself changes, theta to the passage of time, and vega to changes in volatility. Each isolates one reason a premium moves, so together they explain why an option can lose value even when the stock moves your way. They are the vocabulary of managing an option rather than merely buying one.
what is delta in options: Delta is how much an option’s price changes for a one-rupee move in the underlying. A delta of 0.5 means the option gains about ₹0.50 for every ₹1 the stock rises. Delta also approximates the probability the option finishes in the money and tells you the equivalent stock position the option currently behaves like, which is why it is the first greek most traders learn.
what is theta in options: Theta is the rate at which an option loses value simply from time passing, holding everything else constant — the daily cost of time decay. It is negative for an option buyer, who loses a little each day, and positive for the seller, who collects it. Theta accelerates as expiry approaches, which is why out-of-the-money options bleed value fastest in their final days.
why did my option lose money when the stock went up: Usually because another greek moved against you by more than delta helped. If the stock rose only slightly while a day passed, theta’s time decay can outweigh the small delta gain; and if volatility fell at the same time, vega can subtract more still. An option’s price answers to the underlying, time and volatility together, so a favourable move on one can be swamped by the other two.
what is the difference between delta and gamma: Delta measures how much the option price moves when the underlying moves; gamma measures how much delta itself changes as the underlying moves. Delta is the speed, gamma is the acceleration. Gamma is highest for at-the-money options near expiry, which is exactly when an option’s behaviour changes fastest and positions can turn quickly.