TL;DR. A stock option is a time-bound contract that lets you bet on (or hedge against) a stock without owning it. A call is the right to buy at a set price; a put is the right to sell. Every contract has a strike price, an expiration date, and a premium you pay for the right. If the option ends up worthless at expiration, you simply lose the premium — nothing more.
What an option actually is
The SEC defines an option as a contract giving the purchaser “the right – but not the obligation – to buy or sell a security at a fixed price within a specific period of time.” (investor.gov)
Two phrases in that definition do most of the work:
- “Right but not the obligation.” Unlike a futures contract or a stock purchase, the buyer can walk away. If the contract is worthless at expiration, it expires and the buyer loses only what they paid.
- “Within a specific period of time.” Every option ends. The expiration date is fixed at contract inception, after which the right disappears.
In US markets, a single equity option contract represents 100 shares of the underlying stock. So a quote of “$3.20” on a contract means you pay $3.20 × 100 = $320 to own one contract. This 100-share multiplier is one of the most common things new traders get wrong. (Option (finance) reference)
Listed equity options in the United States are a relatively young product. Standardized, exchange-traded options began on April 26, 1973, when the Chicago Board Options Exchange opened and traded 34,599 contracts in its first month. (CBOE history) Today, every listed US options trade clears through the Options Clearing Corporation, which steps in as central counterparty between buyer and seller. (OCC reference)
Calls and puts: the two basic shapes
There are only two kinds of options:
- A call option gives the buyer the right to buy the underlying stock at the strike price on or before expiration. You buy a call when you want upside exposure without putting up the full price of the stock. (OIC: “If you buy a call, you have the right to buy the underlying instrument at the strike price on or before expiration.”)
- A put option gives the buyer the right to sell the underlying stock at the strike price on or before expiration. You buy a put to profit from a fall, or to insure a stock position you already own.
Calls and puts are mirror images: a call is the right to buy, a put is the right to sell. Everything else — spreads, straddles, collars, condors — is built out of those two pieces.
Strike, expiration, premium
- Strike price — the fixed price at which you can exercise. If you own a $200 call, your strike is $200; you can buy shares at $200 regardless of where the stock is trading.
- Expiration date — the last day the contract is alive. Standard US equity options expire on a specific date (often a Friday). After expiration, the contract no longer exists.
- Premium — the price you pay to buy the option (or receive if you sell it). Quoted per share, multiplied by 100 to get the dollar amount per contract.
Premium = intrinsic value + time value
Every option premium has two components:
- Intrinsic value — what the option would be worth if you exercised right now. For a call: max(stock price − strike, 0). For a put: max(strike − stock price, 0). When intrinsic value is positive, the option is “in the money.”
- Time value (or extrinsic value) — everything else in the premium. It reflects the probability the option will finish further in the money before it expires. As expiration approaches, time value erodes toward zero. This is why traders call options “wasting assets.”
The Options Industry Council puts it crisply: “Intrinsic value is the amount that the option is in-the-money… Time value is the difference between the intrinsic value and the premium.” (OIC)
| Contract | Moneyness | Intrinsic value | Time value | Premium (per share) |
|---|---|---|---|---|
| $180 call | Deep ITM | $20.00 | $0.50 | $20.50 |
| $200 call | ATM | $0.00 | $5.00 | $5.00 |
| $220 call | OTM | $0.00 | $1.50 | $1.50 |
| $180 put | OTM | $0.00 | $1.50 | $1.50 |
| $200 put | ATM | $0.00 | $5.00 | $5.00 |
| $220 put | Deep ITM | $20.00 | $0.50 | $20.50 |
A worked example: long call
Suppose Acme Corp trades at $200. You buy one call with a $200 strike, expiring in 30 days, for a premium of $5.00. Total cost: $5.00 × 100 shares = $500.
Three scenarios at expiration:
- Stock at $190. The $200 call is out of the money — worthless. You lose the full $500 premium.
- Stock at $200. The call expires exactly at the strike. Worthless. You lose $500.
- Stock at $215. The call is in the money by $15 per share. Intrinsic value = $15 × 100 = $1,500. Subtract the $500 premium and your net profit is $1,000.
Your max loss is the premium, $500. Your upside is theoretically unlimited because the stock can keep climbing. Breakeven is the strike plus the premium — here, $205.
A worked example: long put
Same stock at $200. You buy one put with a $200 strike for $5.00. Total cost: $500.
- Stock at $210. The put is out of the money. Loss = $500.
- Stock at $200. At the strike. Worthless. Loss = $500.
- Stock at $185. The put is in the money by $15. Intrinsic = $1,500. Net profit = $1,000.
Max loss is the premium. Max profit happens if the stock goes to zero, in which case you collect (strike − premium) × 100 = $19,500. Breakeven is the strike minus the premium — $195.
Moneyness: ITM, ATM, OTM
Traders bucket every option by its relationship to the current stock price:
- In the money (ITM) — intrinsic value is positive. A $180 call when the stock is at $200 is $20 ITM.
- At the money (ATM) — strike is roughly equal to the stock price. Intrinsic value is zero; the entire premium is time value. ATM options have the most time value because the outcome is most uncertain.
- Out of the money (OTM) — strike is on the wrong side of the stock price. A $220 call when the stock is at $200 is $20 OTM. Intrinsic value is zero.
The table above shows how premium splits between intrinsic and time value across those three buckets. Notice that deep-ITM options trade close to pure intrinsic value (almost no time value), while OTM options are pure time value — which is what makes them “cheap” in absolute dollars and dangerous in expected value.
American vs European exercise
Two different exercise styles are common. American-style options can be exercised on any trading day on or before expiration; almost all US-listed equity options are American-style. European-style options can be exercised only at expiration; most US index options (like SPX on the S&P 500) are European-style.
In practice, traders close most positions by selling the contract before expiration rather than physically exercising. Selling captures both intrinsic and remaining time value; exercising captures only the intrinsic value and forfeits any time value left in the contract.
Why people use options
There are four common motivations, each pulling different risk knobs:
- Leverage. A call buyer puts up a fraction of the stock’s price for similar directional exposure. The upside is leverage; the downside is that the option can expire worthless even when the stock barely moves.
- Hedging. A long-stock holder buys puts to cap downside. The put pays off if the stock drops below the strike, like an insurance policy with a deductible (the premium).
- Income. Selling covered calls against a stock you already own generates premium income, in exchange for capping your upside above the call’s strike.
- Speculation on volatility. Combinations like straddles let you bet on how much the stock will move without having a view on direction.
Common beginner mistakes
- Forgetting the 100-share multiplier. A $3 option is a $300 contract. New traders routinely under- or over-size positions because of this.
- Ignoring time decay. Buy a 7-day call and the time value crumbles fast. Buy a 90-day call and the decay is gentler. Same direction, very different P&L.
- Equating “cheap” with “good.” Far-OTM options are cheap because they probably expire worthless. Most do.
- Confusing strike with stock price. The strike is fixed when the contract is written. The stock can be anywhere. Both matter, but for different reasons.
- Holding short calls into expiration ITM. If you’ve sold a call that’s in the money at expiration, you can be assigned and required to deliver shares. Always understand assignment risk before selling options.
What to learn next
Once calls, puts, strikes, and expiration are second nature, the natural next layer is the Greeks: delta (sensitivity to stock price), gamma (sensitivity of delta), theta (time decay), vega (sensitivity to implied volatility), and rho (sensitivity to interest rates). After the Greeks come spreads — combinations of calls and puts at different strikes or expirations that let you express more specific views with capped risk. And underneath all of it sits implied volatility, the market’s forecast for how much the stock will move.
The pattern from here is “more degrees of freedom, more ways to be wrong.” Get fluent in the four building blocks first; everything else is a recombination of them.
Sources
- SEC — Options (investor.gov)
- Options Industry Council — What is an Option?
- Option (finance) — reference
- Chicago Board Options Exchange — reference
- Options Clearing Corporation — reference
Disclosure: This article was produced with AI assistance and reviewed before publication. It is for informational purposes only and is not investment advice.