An option is a derivative contract that gives the buyer a choice: buy or sell an underlying asset at a pre‑agreed price within a set period. You pay a premium for that choice. If the market does not move your way, you can let it lapse and your loss is limited to the premium.
There are two main flavours. A call option gives you the right to buy. A put option gives you the right to sell. The person who sells you the option takes on the obligation to deliver if you exercise.
Strike, expiry and premium: the building blocks
Every option revolves around three terms. The strike price is the level at which you can buy or sell the underlying. The expiration is the last date on which you can exercise your right. The premium is the price you pay (or receive if you write the option) for that right and for the risk the seller takes on.
An option’s premium has two parts. Intrinsic value is the amount you would get from immediate exercise. The rest is time value, which reflects the chance that the option becomes more valuable before it expires. You will often see traders break down a quote into these two pieces to judge how much they are paying for possibility versus certainty. For a deeper definition, see intrinsic value.
Options can be American style, which means you can exercise on any business day up to expiry, or European style, which allows exercise only at expiry. Styles vary by market and underlying, and they affect pricing and strategy.
Calls, puts and what you can do with them
A long call benefits if the underlying rises above the strike before the option runs out of time. A long put benefits if the underlying falls below the strike. Because you control exposure for a fraction of the asset’s price, options give you economic leverage without owning the asset outright.
Common uses include:
- Hedging: buying puts to protect a shareholding from a drop in price.
- Income: selling covered calls against shares you already own to collect premium.
- Speculation: using calls or puts to back a directional view with limited upfront cost.
- Structures: combining options into spreads or straddles to target volatility or define risk.
Option sellers, also called writers, receive the premium but take on an obligation. A covered call writer owns the shares and is prepared to sell them at the strike if assigned. An uncovered or naked writer does not hold the offsetting position and faces higher risk. The margin and eligibility rules for uncovered writing vary by provider and jurisdiction.
Moneyness: in, at or out of the money
Moneyness describes where the market price sits versus the strike. A call is in the money when the underlying is above the strike, at the money when the price and strike are close, and out of the money when the price is below the strike. For puts, flip those relationships. In the money options have intrinsic value, out of the money options are pure time value.
Moneyness shapes behaviour. Deep in the money options move more like the underlying. Out of the money options are cheaper in cash terms but depend heavily on volatility and time remaining.
What moves option prices: time and volatility
Beyond the underlying price, several inputs influence the premium:
- Time to expiry: more time generally means a higher premium, because there is more chance of a favourable move.
- Implied volatility: when the market expects bigger price swings, option prices rise to reflect that uncertainty.
- Interest rates and expected dividends: these can shift the relative value of calls and puts on equities and indices.
Traders manage these sensitivities through the Greeks, a set of risk measures drawn from option pricing models. Delta shows how much the option price should change for a small move in the underlying. Gamma is how fast delta itself changes. Theta captures time decay. Vega measures sensitivity to volatility. Rho links to rates. You do not need to memorise them to use options, but they help explain why the premium moves even when the underlying looks quiet.
How options trade and settle in practice
Options trade on exchanges and, in some markets, over the counter. An exchange will list a series of strikes and expiries, known as an options chain, with bids and offers for each contract. Liquidity varies by strike and date, and the bid‑offer spread is a real cost to factor in. Some contracts have active market makers who quote continuously to keep trading flowing.
Contract size depends on the product. Many equity options represent a fixed number of shares per contract, whereas index and futures options are typically cash settled. Settlement can be physical, where shares change hands if the option is exercised, or cash, where only the profit or loss versus the strike is exchanged. The exact mechanics, including how assignment works for the seller, are set by the listing venue and its clearing house.
Exercise and assignment can happen before expiry on American style options, often around ex‑dividend dates or when little time value remains. If you are short options, monitor early exercise risk. If you are long, weigh the value of immediate exercise against any remaining time value.
Simple payoff examples
Imagine you buy a three‑month call on a share with a strike of 50, paying a premium of 2 per share. If the share finishes at 60 at expiry, you exercise and buy at 50, then could sell at market for 60. The option is worth 10, so your profit is 10 minus the 2 premium, equal to 8 per share. If the share finishes at 48, you let the option expire and lose the 2 premium. Your maximum loss was known from day one.
Now a put. You buy a put with a strike of 50 for a premium of 1.50. If the share ends at 42, the put is worth 8, so your profit is 8 minus 1.50, equal to 6.50 per share. If the share ends above 50, the option expires worthless and your loss is 1.50.
For sellers, reverse the lens. A covered call writer who collected 2 at a 50 strike will be assigned if the share is above 50 at expiry and will deliver shares at 50, keeping the 2 as income. An uncovered short call can face theoretically unlimited losses if the share rallies hard. A short put earns the premium up front but takes on the risk of buying the shares at the strike if assigned, with losses growing as the share falls toward zero.
Common pitfalls and how to avoid them
Time decay is relentless for long options. If the market drifts rather than moves, theta can erode your premium. High implied volatility can make options expensive before an event, then fall sharply after, even if the price move was in the right direction. This is sometimes called a volatility crush.
Liquidity matters. Wide spreads and thin depth can raise trading costs and make exits awkward. Contract specifications vary between venues, so check contract size, settlement type and exercise style before trading. If you sell options, understand margin and assignment. Rules differ by provider and country and can change.
Handled carefully, options let you shape risk rather than simply take it. The contract gives you choice. The craft is knowing what that choice is actually worth and how it behaves as the market shifts and the clock runs down.