What Is an Options Contract?
An option is a contract that gives the buyer the right, but not the obligation, to buy or sell an underlying asset at a fixed strike price on or before expiry. A call is a right to buy and profits when price rises; a put is a right to sell and profits when price falls. The buyer pays a premium for that right, and that premium is the buyer's maximum loss. The Greeks (Delta, Gamma, Theta, Vega) measure what moves the premium.
Think of an option like a token booked for a fixed price. You pay a small fee now for the right to buy at today's agreed price later. If the price rises, the token is valuable; if it does not, you lose only the fee. That limited loss is the main attraction for buyers, and the reason time and volatility work against them.
Index options such as Nifty are cash-settled and European style, meaning they can be exercised only at expiry. Stock options are physically settled. Lot sizes, expiry days and margin rules are revised by the exchange from time to time, so check the current details on the NSE website before trading.
What Are the Key Options Terms?
| Term | Meaning |
|---|---|
| Underlying | The asset the option is based on, such as the Nifty index or a stock |
| Strike price | The fixed price at which the option can be exercised |
| Expiry | The date the contract ends |
| Premium | The price of the option, paid by the buyer to the seller |
| Lot size | The number of units in one contract; multiply per-unit profit or loss by it |
| Buyer (holder) | Pays the premium and has the right to exercise |
| Seller (writer) | Receives the premium and must honour the contract; needs margin |
Options are also described by where the strike sits relative to the current price, called moneyness:
| State | Call option | Put option |
|---|---|---|
| In the money (ITM) | Spot above strike | Spot below strike |
| At the money (ATM) | Spot near strike | Spot near strike |
| Out of the money (OTM) | Spot below strike | Spot above strike |
Call intrinsic value = max(Spot − Strike, 0)
Put intrinsic value = max(Strike − Spot, 0)
Example: with spot at 24,100, a 24,000 call priced at 180 has intrinsic value of 100 and time value of 80. An OTM option has no intrinsic value, so its whole premium is time value, which is why it can decay to zero.
How Do Calls and Puts Make or Lose Money?
At expiry, a bought option's profit is its intrinsic value minus the premium paid. Take a long 24,000 call bought at a premium of 150, per unit:
| Spot at expiry | Intrinsic value | Profit or loss per unit |
|---|---|---|
| 23,700 | 0 | −150 (max loss) |
| 24,000 | 0 | −150 (max loss) |
| 24,150 | 150 | 0 (breakeven = strike + premium) |
| 24,300 | 300 | +150 |
| 24,600 | 600 | +450 |
For a put the logic flips: breakeven is strike minus premium, and profit grows as price falls. Multiply per-unit results by the lot size to get rupee amounts.
Visualising It: Payoff at Expiry for Buyers and Sellers
Buyers have a capped loss and open-ended profit. Sellers have the reverse: capped profit and open-ended loss. BE marks breakeven. Example premiums: call 150, put 120.
What Is the Difference Between Buying and Selling Options?
| Option buyer | Option seller | |
|---|---|---|
| Receives or pays | Pays premium upfront | Receives premium, must post margin |
| Maximum loss | Premium paid | Very large, unlimited for a call |
| Maximum profit | Large, unlimited for a call | Premium received |
| Time decay | Works against the buyer | Works for the seller |
| Needs | Direction, size of move and timing | Price to stay away from the strike |
Sellers win more often but can lose far more when they are wrong, so a seller without a stop-loss or hedge is exposed to a single event wiping out many small gains. Beginners are generally safer starting with defined-risk positions, where the maximum loss is known before entry.
What Are the Option Greeks?
The Greeks are measurements of how an option's premium reacts to different forces. Learn them one at a time.
| Greek | Measures | Long call | Long put | Strongest when |
|---|---|---|---|---|
| Delta | Premium change per 1-point move in the underlying | + (0 to 1) | − (−1 to 0) | Deep in the money |
| Gamma | How fast Delta itself changes | + | + | At the money, near expiry |
| Theta | Premium lost per day from passing time | − | − | At the money, final days |
| Vega | Premium change per 1-point change in implied volatility | + | + | At the money, longer expiry |
| Rho | Premium change per 1-point change in interest rates | + | − | Long expiry; minor for short-dated options |
Option sellers hold the opposite signs: negative Gamma, positive Theta and negative Vega.
What Does Delta Tell You?
Delta is the change in an option's premium for a 1-point move in the underlying. A call with Delta 0.5 gains about 0.5 for each 1-point rise. ATM options sit near ±0.5, deep ITM options approach ±1 and behave like the underlying itself, and far OTM options approach 0. Delta is also a rough guide to the market's estimated chance of the option finishing in the money, though it is an approximation only.
Visualising It: Delta Across Strikes
Call Delta climbs from 0 to 1 as the option goes in the money, and put Delta falls from 0 to −1. Closer to expiry (dashed), the switch is sharper. Illustrative model values, not live prices.
Solid lines: 30 days to expiry. Dashed lines: 3 days to expiry.
What Does Gamma Tell You?
Gamma is how quickly Delta changes as price moves. It is highest for ATM options close to expiry, where a small move can swing an option from nearly worthless to valuable. That is why last-day ATM options can move wildly, both for buyers who gain and sellers who get hurt.
Visualising It: Gamma Peaks at the Strike and Near Expiry
With 3 days left, Gamma spikes at the strike. With 30 days left, it is low and spread out. Illustrative model values, not live prices.
What Does Theta Tell You?
Theta is time decay: the premium an option loses each day, all else equal. Time value does not fade in a straight line. It decays slowly at first and then faster, and fastest in the final week for ATM options. An OTM option decays all the way to zero if it never gets into the money.
Visualising It: Time Decay Speeds Up Near Expiry
The ATM call loses value slowly for weeks and then quickly in the last days. The OTM call fades to zero. Spot fixed at 24,000, volatility 15%. Illustrative model values.
For a buyer, Theta is a daily cost of waiting; for a seller, it is the daily income. This is the main reason buying options on expiry day is such a low-odds game unless the move is large and quick.
What Are Vega and Implied Volatility?
Implied volatility (IV) is the market's expected size of future price swings, backed out of option prices. Vega tells you how much the premium changes for a 1-point change in IV. High IV means expensive options; low IV means cheaper ones. India VIX, computed by the NSE from Nifty option prices, shows the expected annualised Nifty volatility over the next 30 days.
Before events such as results, budgets or policy announcements, IV usually rises and premiums swell. After the event, IV often collapses (sometimes called IV crush), so an option buyer can be right on direction and still lose money because Vega drained the premium.
How Do You Read an Option Chain?
An option chain lists calls on one side, puts on the other and strikes in the middle. Here is a simplified, illustrative chain with spot at 24,000, 7 days to expiry and 14% volatility:
| Call delta | Call premium | Strike | Put premium | Put delta |
|---|---|---|---|---|
| 0.69 | 322 | 23,800 | 92 | -0.31 |
| 0.61 | 257 | 23,900 | 127 | -0.39 |
| 0.53 | 201 | 24,000 | 171 | -0.47 |
| 0.44 | 153 | 24,100 | 223 | -0.56 |
| 0.36 | 114 | 24,200 | 283 | -0.64 |
Illustrative values from a pricing model, not live quotes. The ATM row is in bold.
Notice that call premiums fall as the strike rises while put premiums rise, and that the ATM call and put premiums are of a similar size. Call and put Delta at each strike differ by exactly 1 (for example 0.53 and −0.47 at the 24,000 strike). On a live chain you will also see open interest, volume and implied volatility per strike, and a bid-ask spread. Prefer liquid strikes with a tight spread, since wide spreads are an extra cost.
Common Options Beginner Mistakes
Buying far out-of-the-money "lottery" options
They look cheap because the odds are low. Most of them expire worthless.
Ignoring Theta
Being right on direction is not enough if the move comes too slowly. Time decay eats the premium.
Buying before events at peak IV
Premiums are inflated before news and often fall after, even if the market moves your way.
Selling naked options without a hedge
Small, regular gains can be wiped out by one large adverse move. Define the risk first.
Oversizing positions
Leverage cuts both ways. Risk a small, fixed share of capital per trade.
Trading illiquid strikes
Wide bid-ask spreads make entering and exiting expensive. Stick to actively traded strikes.
Your Options Trade Checklist
Run this five-point check before any options trade:
Direction, size and timing
Do you have a view on which way, how far and by when? Options need all three.
Strike and expiry
Does the strike give a realistic chance of profit, and does the expiry leave enough time?
Implied volatility
Is IV high or low compared with its recent range, and is an event about to change it?
Defined maximum loss
Do you know the most you can lose in rupees, and is it a small share of your capital?
Exit plan
Do you know your profit target, your stop, and when you will exit if time passes without a move?
Educational content only, and options are high risk. This guide explains how options work and is not investment advice or a recommendation to trade. SEBI studies have found that a large majority of individual traders in equity derivatives incur net losses. Never risk money you cannot afford to lose, and check the exchange's current lot sizes, margin rules and expiry schedule before trading.