What Is an Option?
Calls, puts, and why they exist · 15 min
A 2,600-Year-Old Idea
Options are not a modern invention. Around 600 BCE, the Greek philosopher Thales of Miletus predicted a bumper olive harvest based on his study of the stars. He didn't have money to buy olive presses outright, so he paid a small deposit to lock in the right to rent them at a fixed price when harvest season arrived. When his prediction proved correct and demand for presses surged, Thales exercised his right, rented the presses at the agreed price, and sublet them at the higher market rate, pocketing the difference. He had just traded the world's first recorded option.
The modern options market traces to April 26, 1973, when the Chicago Board Options Exchange (CBOE) opened for business — the same year Fischer Black and Myron Scholes published the formula we'll study in Lesson 3. Before the CBOE, options were traded informally between dealers, with no standardized terms and no central clearing. The CBOE introduced standardized contracts, public price quotes, and a clearinghouse that guaranteed both sides. Trading volume on day one: 911 contracts. Today, roughly 40 million options contracts trade daily on U.S. exchanges alone.
The Core Idea
An option is a contract that gives its buyer the right, but not the obligation, to buy or sell an asset at a predetermined price on or before a specified date. Three terms define every option:
- Underlying (S): the asset the option is written on — most commonly a stock, but also an index, ETF, commodity, or currency.
- Strike price (K): the price at which the option holder may buy or sell. Also called the exercise price.
- Expiration date (T): the last date the option can be exercised. After this date it expires worthless if unexercised.
The price paid for the option itself is the premium. This is the most the buyer can ever lose.
Calls and Puts
There are exactly two kinds of options:
- A call option gives the holder the right to buy the underlying at the strike price. Calls profit when the underlying rises.
- A put option gives the holder the right to sell the underlying at the strike price. Puts profit when the underlying falls.
Every option has two parties. The buyer (long) pays the premium and holds the right. The seller (short, or writer) collects the premium and takes on the obligation to fulfill the contract if the buyer exercises.
A Concrete Example
Suppose Apple (AAPL) is trading at $190. You believe it will rise before earnings next month. You buy one call option with:
- Strike: $195
- Expiration: 30 days
- Premium: $4.50 per share
One standard equity option contract covers 100 shares, so you pay $450 total.
Scenario A — AAPL rises to $210 at expiration: You exercise the call, buying 100 shares at $195 and immediately selling them at $210. Gross profit: $1,500. Subtract the $450 premium. Net profit: $1,050 — a 233% return on your $450 outlay.
Scenario B — AAPL stays at $190 at expiration: The call expires worthless. You lose your entire $450 premium. The stock moved against you, but your maximum loss was capped at the premium — not the full $19,000 you'd have lost buying 100 shares.
This asymmetry is the fundamental appeal of options: limited downside, leveraged upside.
American vs. European Options
Options come in two exercise styles:
- American options can be exercised at any time before expiration. Most stock options traded on U.S. exchanges are American-style.
- European options can only be exercised at expiration. Most index options (SPX, NDX) are European-style. The Black-Scholes formula we'll derive in Lesson 3 is technically for European options.
The ability to exercise early is almost always worth something for put options (especially deep in-the-money puts) but rarely worth much for calls on non-dividend stocks. We'll revisit this in the Binomial Trees lesson.
Intrinsic Value vs. Extrinsic Value
An option's premium decomposes into two components:
- Intrinsic value is what you'd capture if you exercised right now. For a call: max(S − K, 0). For a put: max(K − S, 0). It can never be negative.
- Extrinsic value (also called time value) is everything else. It reflects the probability that the option will gain more intrinsic value before expiry, driven by time remaining and volatility.
Example: AAPL at $190, call with K = $185 trading at $9.00. Intrinsic value = $5.00. Extrinsic value = $4.00. An option always trades at or above intrinsic value — otherwise there's an immediate arbitrage.
Moneyness
Moneyness describes where the current stock price sits relative to the strike:
- In-the-money (ITM): the option has positive intrinsic value. Call: S > K. Put: S < K.
- At-the-money (ATM): S ≈ K. Intrinsic value is approximately zero but extrinsic value is at its maximum for a given expiry.
- Out-of-the-money (OTM): intrinsic value is zero. Call: S < K. Put: S > K. Pure time value — essentially a bet that the stock will move enough.
Deep OTM options are cheap in absolute terms but highly leveraged. A $0.10 option that pays off $5 delivers a 50x return. They are also the most likely to expire worthless — over 70% of options held to expiration expire with zero value according to CBOE data.
Why Options Exist
Three legitimate uses drive the options market:
- Hedging: A portfolio manager owning 10,000 shares of Apple might buy puts to protect against a crash — paying a small premium to cap downside losses. This is portfolio insurance.
- Speculation: Traders use options to express directional or volatility views with defined risk and high leverage.
- Income generation: Shareholders sell covered calls against stock they own, collecting premium as income in exchange for capping their upside.
Understanding which use case a trade serves is critical to evaluating whether it makes sense. The same instrument — a put option — can be portfolio insurance for a hedger, a speculative short bet for a directional trader, or a cash-secured income trade for a seller.