Options Contract Mechanics

A stock buys you a piece of a business. An options contract buys you a piece of a bet on a price - one with a deadline, a strikeStrike priceThe price at which an option can be exercised. For a call, it's the buy price; for a put, the sell price.Read in glossary →, and a multiplier that quietly turns small numbers into real money. This first lesson is about the plumbing: what you actually own when you buy a call or a put, what the quoted premium is paying for, and the four contract specs that decide whether your trade can survive the bid/ask before it sees the first tick.

What an options contract actually is

An options contract is a legal agreement between two parties: a buyer and a seller. The buyer pays the seller an upfront premiumPremiumThe price paid (or collected) to enter an options contract. Equal to intrinsic value plus extrinsic (time + volatility) value.Read in glossary → today. In exchange, the buyer gets the right but not the obligation to either buy (a callCallAn options contract giving the buyer the right but not the obligation to buy 100 shares of the underlying at the strike price on or before expiration.Read in glossary →) or sell (a putPutAn options contract giving the buyer the right but not the obligation to sell 100 shares of the underlying at the strike price on or before expiration.Read in glossary →) 100 shares of a specific stock, at a specific price (the strike), on or before a specific date (expiration). The seller, having taken the cash, takes on the obligation to be on the other side if the buyer chooses to exerciseExerciseConverting an option into the underlying stock position at the strike price. Long calls exercise into stock; long puts exercise into a short stock position (or sell existing shares).Read in glossary →.

That's the whole instrument. Three numbers - strike, expiration, premium - and a direction (call or put). Everything else in options trading is mechanics, math, and strategy stacked on top of that primitive.

A few consequences fall out of the definition immediately:

• The buyer's risk is bounded at the premium paid. The worst case is the option expires worthless and the premium is lost.
• The seller's risk is potentially unbounded (for naked calls) or substantial (for naked puts). The seller has the obligation; the buyer has the choice.
• Time is one-directional. Every day that passes erodes the buyer's flexibility and the seller's risk. This single asymmetry is the source of thetaThetaThe daily decay of an option's extrinsic value. Negative for long options (buyer's tax), positive for short options (seller's carry). Accelerates inside the last 30 - 45 days.Read in glossary →, which we'll cover in lesson 3.

The four contract specs that matter

Every listed option in the U.S. equities market has the same four specs. Read them right and you know exactly what you are trading.

The convention to read a quote: AAPL Jun 21 195 Call @ $4.20. That's an Apple call expiring June 21, with a $195 strike, trading at $4.20 of premium per share. One contract represents 100 shares, so the cash to open one contract is $4.20 × 100 = $420. The multiplier is the single most-skipped step new traders make - quotes always look "small" until you remember to multiply.

Premium = intrinsic + extrinsic

The quoted premium of an option is always the sum of two parts:

Intrinsic valueIntrinsic valueThe portion of an option's premium that would be realized if exercised immediately. Call: max(stock − strike, 0). Put: max(strike − stock, 0).Read in glossary → is what the option would be worth if you exercised it right now and immediately closed the resulting stock position. For a call: max(stock - strike, 0). For a put: max(strike - stock, 0). It can never be negative. It's the floor.

Extrinsic valueExtrinsic valueThe portion of an option's premium beyond intrinsic value. Driven by time remaining and implied volatility; decays toward zero by expiration.Read in glossary → (also called time value) is everything else. It's what the market is paying for the possibility that the option will move further into the money before expiration. Extrinsic value is driven by two things: time remaining (more days = more possibility) and implied volatility (more uncertainty = more possibility). It is always non-negative and decays toward zero as expiration approaches.

A worked example. Apple is at $200. You look at the AAPL Jun 21 195 Call:

• Strike $195, stock $200 → call is in-the-money (ITM) by $5
• Premium quoted at $7
• Intrinsic value = $200 - $195 = $5
• Extrinsic value = $7 - $5 = $2

The market is charging you $2 of extrinsic on top of $5 of intrinsic. That $2 is the price of optionality - the possibility AAPL keeps moving up between now and June 21. If AAPL stays at $200 and you hold to expiration, the $2 of extrinsic decays to zero and your $7 option is worth exactly $5 at expiry. You lose the $2 to time decay and break even net of commissions only if the stock moves enough to offset.

In, at, and out of the money

Three labels everyone uses, defined relative to the current stock price:

• ITM (in-the-money): the option has intrinsic value. For a call: stock > strike. For a put: stock < strike.
• ATM (at-the-money): strike ≈ stock. By convention, the closest listed strike to the current stock price.
• OTM (out-of-the-money): the option has zero intrinsic value, only extrinsic. Stock < strike (call) or stock > strike (put).

These labels matter because they predict how the option behaves:

• Deep ITM options behave like the stock itself. A call $30 ITM with a few weeks to expiry has delta near 1.0 - it moves dollar-for-dollar with the underlying. Almost all premium is intrinsic; very little is extrinsic.
• ATM options have the highest extrinsic value and the highest gamma. They move ~50 cents on the dollar with the stock and are the most sensitive to volatility.
• OTM options are 100% extrinsic - pure lottery tickets. They're cheap, decay fast, and require the stock to move and arrive at the strike before expiration to pay off.

Lesson 2 covers strike selection in depth. For now, the takeaway is: the label tells you what's inside the premium and how it'll behave under price moves.

Expiration mechanics: weeklies, monthlies, LEAPS

Every option has an expiration date. Listed equity options expire at the close of business (4:00 p.m. ET) on their stated date, after which they're automatically exercised if ITM by more than $0.01 or expire worthless if OTM. The expiration calendar has three families:

Monthlies are by far the most liquid and have the tightest spreads - the default for most strategies. Weeklies are used when you want to pin a specific event. LEAPS are used when you want long exposure with options leverageLeverageControlling a larger position than your capital alone would allow. 2× leverage means a 1% move produces 2% P&L.Read in glossary → but minimal short-term decay. 0DTE deserves its own warning, covered in lesson 9.

American vs European exercise style

U.S. listed equity options are American-style - the buyer can exercise any time before expiration. Index options like SPX and NDX are European-style - exercise only at expiration. The practical differences:

• American has a small early-exercise risk. A short ITM call can be assigned at any time, especially around ex-dividend dates (the buyer wants the dividend; if the call's extrinsic value is less than the dividend, exercising early captures it). This is rare but real.
• European simplifies pricing - no early-exercise premium to model. Cash-settled at expiration based on the official closing print.

For a beginner trading equity options, the practical rule is: don't be short ITM calls the day before ex-dividend unless you've thought through the assignmentAssignmentThe process by which a short option holder is required to fulfill the contract - delivering shares (short call) or buying them (short put). Auto-triggered by the OCC for ITM options at expiration.Read in glossary → math. Lesson 9 covers assignment mechanics in detail.

The bid/ask spread is the real cost

Every option has two quoted prices: the bidBidThe highest price a buyer is currently willing to pay. When you sell with a market order, you sell at the bid.Read in glossary → (what someone will pay you to sell to them) and the askAskThe lowest price a seller is currently willing to accept. When you buy with a market order, you buy at the ask.Read in glossary → (what someone will charge you to buy from them). The difference is the spreadSpreadThe difference between the best ask and best bid. Effectively the round-trip cost paid to market makers on every trade.Read in glossary →, and on options, it's often the single largest cost of the trade.

If you buy at the ask and sell at the bid, the round-trip costs you the full spread - and that comes out of your edge before the underlying does anything. A $5 option with a $0.50 spread has bled 10% of itself before the trade has even moved. Stack two trades a week of that and the spread alone can erase the strategy.

The implication: liquidity is a feature, not a constraint. The most consistently profitable retail options traders concentrate on a small handful of liquid underlyings (SPY, QQQ, IWM, large-cap megas) and the front two monthly expirations. Far-dated, far-OTM, low-volume names look enticing because they're "cheap" - they're cheap because the spread will eat the trade.

The chain above is illustrative - it shows you the structure of a typical options chain for a stock at $200 with 30 days to expiration. Real chains add open interest, volume, and last-price columns, but the core columns are the same: bid, ask, delta, IV. The ATM strike is highlighted because most beginners' attention should start there.

How to read a real quote

Putting it all together. Suppose AAPL is at $200 and you're looking at the AAPL May 17 200 Call quoted at:

• Bid: $4.10
• Ask: $4.25
• Last: $4.20
• Implied vol: 26%
• DeltaDeltaHow much an option's price changes per $1 move in the underlying. Also a working approximation of the probability the option finishes ITM at expiration.Read in glossary →: 0.52
• Open interest: 18,400

What you'd say in plain English: "The market is pricing the right to buy 100 shares of Apple at $200 between now and May 17 at $4.10 - $4.25 per share. To open one contract long, I'd pay $425 (100 × $4.25). The contract is roughly at-the-money - delta 0.52 means it'll move ~52 cents for every $1 move in AAPL on a near-term basis. Implied vol of 26% is the market's annualized expectation of how much AAPL will move; lesson 4 will tell us whether that's high or low for AAPL. Open interest of 18,400 contracts confirms this strike is liquid - I should be able to fill near mid."

That's the entire reading exercise. Strike, expiration, premium, multiplier, the breakdown into intrinsic and extrinsic, and a glance at delta and IV for behavior. From here, every lesson in this track is layering more precision onto that same picture.

What to take with you

• One contract = 100 shares. The premium quote is per share. Always multiply.
• Premium = intrinsic + extrinsic. Intrinsic is what's already there. Extrinsic is what you pay for the possibility of more.
• ITM, ATM, OTM aren't just labels - they predict behavior. Lesson 2 maps that to strike selection.
• Liquidity is a feature. A wide spread is a hidden cost that compounds across every trade. Stick to liquid underlyings until you're sized to where the spread doesn't dominate.
• Time is one-directional. Every day reduces extrinsic value. Lesson 3 makes that math explicit through theta.

In the next lesson, we'll use this foundation to make the most-asked beginner question - which strike do I pick? - actually answerable.