Derivatives
Call and put options, explained
An option gives its holder the right — but not the obligation — to buy or sell something at a fixed price, by a fixed date. That single idea, "the right but not the obligation," is the key to the entire world of options.
Options sound intimidating, but the core concept is intuitive. You’re paying a small amount now for the choice to make a trade later — a choice you’ll only use if it works in your favour. There are two basic flavours: calls and puts.
The call option: the right to buy
A call option gives its buyer the right to buy the underlying asset at a fixed price — the strike price — on or before the expiry date. The buyer pays a fee upfront, called the premium, for that right.
If the asset’s price rises above the strike, the call is worth using: the holder can buy cheap and is "in the money," profiting by the difference minus the premium. If the price stays below the strike, they simply let the option expire — and the most they can lose is the premium they paid. The seller of the call takes the opposite side: they pocket the premium, but carry the risk of having to sell at the strike price no matter how high the asset climbs.
The put option: the right to sell
A put option is the mirror image — it gives the buyer the right to sell the underlying at the strike price. Puts make money when prices fall. If the asset drops below the strike, the put is in the money; if it rises above, the put expires worthless and again the buyer loses only the premium.
This makes puts the classic hedge. An investor holding shares can buy puts to cap their downside: if the market tumbles, the puts pay out and cushion the loss; if it rises, the shares gain and all that was lost is the small premium. It’s a bit like insurance on a portfolio.
Moneyness: where the price sits
Moneyness just describes where the current price is relative to the strike:
- In the money (ITM) — exercising now would be profitable.
- At the money (ATM) — the price is roughly at the strike.
- Out of the money (OTM) — exercising now would not pay.
There’s also a difference in when you can exercise: European options can only be exercised at expiry, while American options can be exercised any time up to it. Most stock-index options are European; most single-stock options in the US are American.
Intrinsic value vs time value
An option’s premium is made of two parts:
- Intrinsic value — what it’s worth if exercised right now. An out-of-the-money option has zero intrinsic value.
- Time value — the extra premium reflecting the chance the option moves further into the money before it expires.
Time value bleeds away as expiry approaches, and that decay speeds up near the end. It’s why an at-the-money option can still carry a meaningful price despite having no intrinsic value — there’s still time for it to go either way. Options are a natural next step once you understand risk and return, because they let you shape a payoff precisely.
Key takeaways
- An option is the right, not the obligation, to buy or sell at a set strike price.
- A call profits when prices rise; a put profits when they fall.
- An option buyer’s maximum loss is the premium paid.
- Premium = intrinsic value + time value, and time value decays toward expiry.
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