What Are Options? Types and How They Work

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An option is a contract that gives its buyer the right, but not the obligation, to buy or sell a specific underlying asset at a fixed price (the strike price) on or before a set date (the expiration date). The buyer pays a price, called the premium, for that right. The seller, called the writer, collects the premium and takes on the matching obligation: to sell the asset (for a call) or buy it (for a put) at the strike price if the buyer chooses to exercise.

That asymmetry is what defines options in finance. The buyer can walk away and lose only the premium. The seller cannot walk away and may lose far more than the premium collected. Every other feature (pricing, the Greeks, spreads, hedging) follows from it.

What Is an Option?

An option has five defining parts:

1. The underlying: the asset the contract refers to, such as shares of a company, an equity index, an exchange-traded fund, a futures contract or a currency pair.
2. The type: call (right to buy) or put (right to sell).
3. The strike price: the fixed price at which the underlying can be bought or sold. It is also called the exercise price.
4. The expiration date: the last day the right exists. After that, the contract ceases to exist.
5. The premium: the price the buyer pays the seller for the contract.

The buyer is the holder or long side; the seller is the writer or short side. Each contract therefore creates two opposite positions: a call buyer benefits if the underlying rises, a put buyer benefits if it falls, and each writer benefits if that move does not happen.

Options terminology to know

• Exercise: the holder using the right to buy or sell at the strike price.
• Assignment: the notice a writer receives when a holder exercises, which triggers the writer’s obligation.
• In the money (ITM): an option with intrinsic value. A call is ITM when the strike is below the underlying price; a put is ITM when the strike is above it.
• At the money (ATM): an option whose strike equals, or is very close to, the current price of the underlying.
• Out of the money (OTM): an option with no intrinsic value, only time value. A call is OTM when the strike is above the underlying price; a put is OTM when the strike is below it.
• Implied volatility (IV): the volatility of the underlying implied by the option’s market price, expressing how large the market expects future moves to be.
• Open interest: the number of contracts outstanding that have not been closed, exercised or expired. Together with daily trading volume, it shows how actively a given contract trades.

How Options Work

Contract size and what the premium really costs

Premiums are quoted per unit of the underlying, but contracts are traded in fixed sizes. A standard US-listed equity option covers 100 shares. A premium quoted at $0.35 therefore costs $35 per contract ($0.35 × 100), before commissions and fees. A premium quoted at $4.10 costs $410 per contract.

The multiplier scales profits, losses, the obligation of a writer and the share-equivalent exposure measured by delta. Index options, options on futures and currency options use their own contract specifications, so the multiplier has to be read from the specific contract rather than assumed.

Expiration cycles

Depending on the underlying, listed options can expire daily, weekly, monthly or quarterly. Standard monthly US equity options usually expire on the third Friday of the month. More time means more opportunity for the underlying to move, so a longer-dated option is generally more expensive than an otherwise identical shorter-dated one.

Three ways a position ends

1. Closing before expiration. The holder sells the option back to the market, or the writer buys it back. Many option positions end this way, with the trader keeping or paying the difference between the opening and closing premium. No shares change hands.
2. Exercise and assignment. The holder exercises, and the clearing system assigns a writer, who must then deliver (call) or take delivery of (put) the underlying at the strike price. Some contracts, such as many index options, settle in cash instead of delivering the underlying.
3. Expiration. If the option is out of the money at expiration, it expires worthless. The holder loses the premium and the writer keeps it.

Where options trade

Options trade in two kinds of markets. Listed (exchange-traded) options have standardized strikes, expirations and contract sizes. A trader places the order through a broker, but the trade is executed on an exchange and cleared by a central clearinghouse (in the US, the Options Clearing Corporation). The clearinghouse becomes the counterparty to both sides, so the buyer does not depend on the specific seller who wrote the contract.

Over-the-counter (OTC) options are negotiated directly between two parties, often a bank and a client. Terms can be customized (any strike, any date, any notional amount), but each side carries the credit risk of the other. Much of the currency options market is OTC, alongside listed currency options on exchanges.

Intrinsic value and time value

Every premium can be split into two parts:

Premium = intrinsic value + extrinsic (time) value

Intrinsic value is what the option would be worth if exercised immediately:

• Call intrinsic value = max(0, underlying price − strike price)
• Put intrinsic value = max(0, strike price − underlying price)

Extrinsic value is the remainder. It reflects the chance that the option becomes more valuable before expiration, so it depends on time remaining, implied volatility and interest rates. An OTM option is made entirely of extrinsic value.

Hypothetical example: a stock trades at $54. A $50-strike call has $4 of intrinsic value. If the call’s premium is $5.50, its time value is $1.50. A $56-strike call on the same stock has zero intrinsic value, so its entire premium is time value.

Time value decays toward zero as expiration approaches. At expiration, an option is worth only its intrinsic value. This is why a holder can be right about direction and still lose money: if the underlying moves too little or too late, the decline in time value can outweigh the gain in intrinsic value.

Types of Options

Call options

A call option gives the holder the right to buy the underlying at the strike price on or before expiration. A call becomes more valuable as the underlying rises, so calls have a positive delta.

A long call is a bullish position: its maximum loss is the premium paid, and its upside is, in theory, unlimited.

Put options

A put option gives the holder the right to sell the underlying at the strike price on or before expiration. A put gains value as the underlying falls, so puts have a negative delta. Economically, a long put behaves like a short position in the underlying, but with the loss capped at the premium.

Puts are also used as insurance. An investor who owns shares can buy a protective put to set a floor under the position: whatever happens to the share price, the investor can sell at the strike price until the put expires.

American vs. European options

The difference between American and European options concerns when the holder can exercise, not where the option trades.

• American-style options can be exercised on any trading day from purchase through expiration.
• European-style options can be exercised only at expiration.

In the US, most single-stock options are American-style, while many index options are European-style. Because early exercise is a feature the holder can use, an American option is worth at least as much as an otherwise identical European option, and its premium is often higher.

The practical consequence falls mostly on writers. A writer of an American-style option can be assigned before expiration, for example when a short call is deep in the money just before the underlying pays a dividend. A writer of a European-style option knows assignment can come only at expiration. There are also hybrid styles, such as Bermudan options, which can be exercised on a set of specific dates before expiration; these are mostly found in OTC markets.

Types of options by underlying

Calls and puts exist on many kinds of assets. The mechanics are the same, but the details of settlement and contract size differ.

• Equity options: on shares of individual companies, usually covering 100 shares and settled by delivering the shares.
• Index options: on an equity index. They typically settle in cash because an index cannot be delivered.
• ETF options: on exchange-traded funds. They usually settle in ETF shares, unlike most index options.
• Options on futures: the underlying is a futures contract. Exercising a call on a futures contract results in a long futures position at the strike price.
• Currency (FX) options: the right to exchange one currency for another at a fixed exchange rate. A EUR/USD call is the right to buy euros and sell US dollars at the strike rate, which is the same thing as a put on US dollars against euros. FX options are traded OTC and on exchanges.
• Interest rate and bond options: on bonds, rates or rate futures, used to hedge or take positions on borrowing costs.
• Commodity options: most often written on commodity futures, such as oil or gold futures.

Beyond these standard (“vanilla”) contracts, there are exotic options with modified payoffs, such as barrier options that activate or cancel if the underlying touches a level, or Asian options that pay based on an average price. Exotics are mostly OTC.

Options a company issues vs. options others trade

Two products share the name but work differently. Employee stock options and warrants are issued by the company itself: when they are exercised, the company typically issues new shares and receives the strike price. Listed options on a company’s stock are created by investors trading with each other. When a listed option on a stock is bought, sold or exercised, the money moves between option holders and writers, not to the company. The company does not receive premiums from that trading.

The Four Basic Option Positions

Every options strategy, however complicated, is built from four positions. The formulas below give profit or loss at expiration, per unit of the underlying, before commissions. Multiply by the contract size and number of contracts for the dollar result. S is the underlying price at expiration, K is the strike and P is the premium.

Buying a call (long call)

Profit = max(0, S − K) − P

The buyer expects the underlying to rise above the strike by more than the premium. If S finishes above K, the holder can exercise or simply sell the option before expiration. If S finishes at or below K, the option expires worthless and the loss equals the premium.

• Maximum loss: the premium paid
• Maximum gain: unlimited in theory
• Breakeven: K + P

Selling a call (short call)

Profit = P − max(0, S − K)

Selling an option is called writing it. The call writer collects the premium and expects the underlying to stay at or below the strike. If it does, the option expires worthless and the writer keeps the premium, which is the maximum profit.

If the underlying finishes above the strike, the writer must sell the underlying at the strike price, either from shares already owned or by buying them at the higher market price. A writer who does not own the underlying (a naked or uncovered call) faces losses that grow without limit as the price rises. A writer who owns the shares (a covered call) gives up gains above the strike but does not face that open-ended loss, because the shares can be delivered.

• Maximum gain: the premium received
• Maximum loss: unlimited for an uncovered call
• Breakeven: K + P

Buying a put (long put)

Profit = max(0, K − S) − P

The put buyer expects the underlying to fall below the strike by more than the premium. If it does, the holder can exercise and sell the underlying at the higher strike price, or sell the put itself. If the underlying finishes at or above the strike, the put expires worthless.

• Maximum loss: the premium paid
• Maximum gain: K − P, reached if the underlying falls to zero
• Breakeven: K − P

Selling a put (short put)

Profit = P − max(0, K − S)

The put writer is bullish or neutral: they expect the underlying to stay at or above the strike. If it does, the put expires worthless and the writer keeps the premium.

If the underlying falls below the strike, the writer must buy it at the strike price, which is now above the market price, and the loss grows as the underlying falls, offset by the premium received. After assignment, the writer can hold the shares or sell them and take the loss.

Some investors write puts deliberately at a strike where they would be willing to own the asset. If the price falls and they are assigned, they buy at a price they had already chosen, effectively reduced by the premium they collected. If the price does not fall, they keep the premium.

• Maximum gain: the premium received
• Maximum loss: K − P, reached if the underlying falls to zero
• Breakeven: K − P

Comparing the risk on each side

In exchange for this larger risk, writers collect premium up front and profit in more scenarios (the underlying moving against the buyer, not moving, or not moving enough). For this reason brokers typically require margin for short option positions and apply stricter approval levels to them.

Worked Example: Options vs. Owning Shares

The following example is hypothetical and uses round numbers to show the mechanics. It ignores commissions and assumes each contract covers 100 shares.

A long call compared with buying the stock

Stock XYZ trades at $50. A trader who expects it to rise has two choices:

• Buy 100 shares for $5,000.
• Buy one one-month call with a $52 strike for a premium of $1.20, costing $120.

The call’s breakeven at expiration is $53.20 ($52 + $1.20). Here is how the two choices compare at expiration under three outcomes:

XYZ rises to $56. The call is worth $4 ($56 − $52), or $400 per contract. Profit: $400 − $120 = $280, a 233% return on the $120 paid. The shares gain $600 on $5,000, a 12% return. The shares make more dollars; the call makes a much higher percentage on a much smaller outlay.

XYZ stays at $50. The call expires worthless and the trader loses $120, or 100% of the premium. The shares are unchanged, with no loss.

XYZ falls to $45. The call still loses only $120. The shares lose $500.

This is the leverage that makes options attractive and dangerous at the same time: a large percentage gain on a moderate move, a dollar loss capped at the premium, and a total loss if the move does not happen before expiration. A stockholder can wait out a flat month; a call holder cannot.

A protective put on shares already owned

Now suppose an investor already owns 100 shares of XYZ bought at $50 and wants protection for two months. They buy one $47-strike put for $0.90, costing $90.

If XYZ falls to $40, the shares lose $1,000. The put is worth $7 ($47 − $40), or $700, for a net gain on the put of $610. The combined loss is $390, which equals the distance to the strike ($3 × 100 = $300) plus the premium ($90). No matter how far the stock falls before expiration, the loss is capped at $390.

If XYZ rises to $58, the put expires worthless. The shares gain $800, and the investor’s net gain is $710 after the $90 cost of protection.

What Determines an Option’s Price

An option’s premium depends on six inputs:

1. Underlying price: a higher price raises call values and lowers put values.
2. Strike price: a lower strike makes a call more valuable; a higher strike makes a put more valuable.
3. Time to expiration: more time generally raises the value of both calls and puts.
4. Volatility: higher expected volatility raises the value of both calls and puts, because larger moves increase the chance of finishing deep in the money while the holder’s loss stays capped at the premium.
5. Interest rates: higher rates tend to raise call values and lower put values.
6. Dividends (for stock options): expected dividends lower call values and raise put values, because the share price typically drops by about the dividend when the stock goes ex-dividend.

Of these, volatility is the only input that cannot be observed directly. Pricing models take the other five as given; the market price of the option then reveals the volatility the market is assuming, which is the implied volatility. Two options on the same underlying can therefore be “cheap” or “expensive” in a way that has nothing to do with their dollar premium.

The best-known pricing framework is the Black-Scholes model, published in 1973, which prices European options under a set of simplifying assumptions. Binomial models, which step the underlying price through a tree of possible paths, handle American-style early exercise. Currency options are commonly priced with an adaptation of Black-Scholes that accounts for the interest rates of both currencies.

For European options on a non-dividend-paying asset, call and put prices are linked by put-call parity:

Call − Put = Underlying price − Present value of the strike

If the relationship breaks, an arbitrage exists, so in practice it keeps calls and puts with the same strike and expiration in line with each other.

The Greeks: Measuring Option Risk

The Greeks describe how sensitive an option’s price is to each input, assuming the others stay constant. Traders use them to understand individual positions and to manage the combined risk of a portfolio of options.

Delta

Delta (Δ) is the expected change in the option’s price for a $1 change in the underlying. Call deltas range from 0 to 1, and put deltas range from 0 to −1. Roughly, an ATM option has a delta near 0.50 (or −0.50 for a put), ITM options have deltas further from zero, and OTM options have deltas closer to zero.

Example: a call with a delta of 0.50 should gain about $0.50 if the underlying rises $1, all else equal.

Delta also measures net share exposure, the number of shares a position behaves like:

Share-equivalent exposure = delta × contract size × number of contracts

Three calls with a delta of 0.40 on 100-share contracts behave like a long position of 120 shares (0.40 × 100 × 3). Two puts with a delta of −0.30 behave like a short position of 60 shares. Adding up these figures across a portfolio gives its net delta, and that is the hedge ratio: to make the three-call position delta neutral, the trader would sell 120 shares.

Delta is sometimes read as a rough probability that the option expires in the money, so a 0.40-delta call is treated as having about a 40% chance. This is an approximation from pricing models, not a precise forecast.

Gamma

Gamma (Γ) is the change in delta for a $1 change in the underlying. It is a second-order sensitivity: delta measures how the price changes, gamma measures how delta itself changes.

Example: a call has a delta of 0.50 and a gamma of 0.10. If the underlying rises $1, delta increases to about 0.60; if it falls $1, delta drops to about 0.40.

High gamma means delta can swing sharply on small moves in the underlying, so a hedge that was correct a moment ago may no longer be. Gamma is highest for ATM options and rises as expiration approaches; long-dated options have smaller gamma and steadier deltas. Option buyers have positive gamma, while sellers have negative gamma. Traders who hedge both delta and gamma (delta-gamma neutral) keep their net delta close to zero as the underlying moves.

Theta

Theta (Θ) is the change in the option’s price as one day passes, all else equal. It measures time decay.

Example: an option with a theta of −0.05 loses about $0.05 per day, or $5 per day on a 100-share contract. Over three days, all else unchanged, it loses about $0.15.

Theta is usually largest for ATM options, and time decay accelerates as expiration approaches. Long calls and long puts generally have negative theta: time works against the holder. Short calls and short puts have positive theta: time works for the writer. This is the trade-off at the center of options: buyers pay for time and convexity (positive gamma), sellers are paid to take on the risk of large moves.

Vega

Vega measures the change in the option’s price for a one-percentage-point change in implied volatility.

Example: an option with a vega of 0.10 should gain about $0.10 if implied volatility rises from 25% to 26%, and lose about $0.10 if it falls to 24%.

Long options have positive vega, and vega is largest for ATM options with a long time to expiration. A buyer can be right about direction and still lose if implied volatility falls sharply, for instance after a scheduled event such as an earnings release has passed.

Rho

Rho (ρ) measures the change in the option’s price for a one-percentage-point change in interest rates.

Example: a call priced at $1.25 with a rho of 0.05 would rise to about $1.30 if rates rose by one percentage point, all else equal. A put’s rho is negative, so the same rate rise would lower the put’s value.

Rho is usually the least important Greek for short-dated contracts and matters more for long-dated options. For currency options, the interest rates of both currencies enter the price.

How Options Are Used

Speculation with defined risk

Buying calls or puts lets a trader take a directional view for a fraction of the cost of buying or shorting the underlying, with the maximum loss known at the outset, as the worked example shows.

Hedging

Options can reduce risk on positions a trader already holds. A protective put sets a floor under shares owned. A currency option lets a business fix a worst-case exchange rate for a future payment while keeping the benefit if the rate moves in its favor. An investor with heavy exposure to one company can also sell calls against the shares to collect premium and reduce the effective cost basis, accepting a cap on gains.

Income

Writing options produces premium income. Common approaches are covered calls (selling calls against shares owned), which give up part of the upside, and cash-secured puts (selling puts with enough cash set aside to buy the shares if assigned), which accept the obligation to buy on a decline.

Spreads and combinations

Spreads combine bought and sold options on the same underlying to shape a specific risk and reward profile. Some common structures:

• Vertical spreads: buy one option and sell another of the same type and expiration at a different strike. A bull call spread (buy a lower-strike call, sell a higher-strike call) costs less than a single call but caps the gain. These are classed as debit spreads (net premium paid) or credit spreads (net premium received).
• Straddles: buy a call and a put at the same strike and expiration, profiting from a large move in either direction. Strangles do the same with different strikes, costing less but needing a larger move.
• Iron condors and butterfly spreads: combine several strikes to profit if the underlying stays in a range, with defined maximum gain and loss.
• Collars: own the shares, buy a protective put and sell a call to help pay for it, limiting both the loss and the gain.

Spreads are usually described by their payoff diagrams, which plot profit or loss at expiration against the underlying price. Because some legs are sold, spreads typically involve margin and assignment risk on the short legs.

Limitations and Risks of Options

• Complexity. An option’s value depends on several inputs at once, including one (volatility) that is not directly observable.
• Time decay and total loss. Long options lose time value every day. Losing 100% of the premium is a normal outcome for an option buyer, not an extreme scenario.
• Large losses for writers. An uncovered call has no maximum loss, and writers can lose many times the premium collected.
• Leverage cuts both ways. The same feature that magnifies percentage gains magnifies percentage losses.
• Early assignment. Writers of American-style options can be assigned before expiration, which can leave them unexpectedly long or short the underlying.
• Liquidity and spreads. Contracts with little trading volume or open interest can have wide bid-ask spreads, so the cost of getting in and out eats into returns.
• Counterparty risk in OTC options. Without a clearinghouse, the holder depends on the writer’s ability to pay.

Because of these features, US brokers generally require clients to apply for options trading and assign approval levels, with uncovered writing at the highest level.

Options vs. Related Instruments

Options vs. futures

Both options and futures are derivatives on an underlying asset, and both have expiration dates. The defining difference is obligation. A futures contract obligates both sides to buy or sell the underlying at the agreed price on the settlement date. An option obligates only the writer; the buyer has a right that can be left unused.

That changes the risk profile. A futures buyer gains or loses roughly one-for-one with the underlying in both directions and pays no premium up front, though margin is required. An option buyer pays a premium and has an asymmetric payoff: open-ended gain in one direction, loss capped at the premium in the other.

Options vs. owning the underlying

Owning shares has no expiration and no time decay; a shareholder can wait indefinitely and receives dividends and voting rights. An option holder has none of those and must be right within a deadline, but controls the same exposure for less capital and, as a buyer, with a defined maximum loss.

Options vs. forwards in currency hedging

A forward fixes an exchange rate in both directions at no up-front cost. A currency option fixes only the worst case and leaves the favorable side open, at the cost of a premium. The choice between them is a choice between certainty and flexibility.

FAQs

The Bottom Line

Options matter to anyone weighing a directional trade, a hedge or premium income on stocks, indexes, futures or currencies. Buyers risk only the premium but must be right before expiration, while writers collect premium in exchange for obligations that can bring losses far larger than that premium. Understanding contract size, time decay and assignment rules comes before choosing which side of the contract to take.