How to Use This Glossary
Options vocabulary is unusually slippery. The same word means one thing in a textbook and something narrower on a trading desk — “premium” is the price of a contract to a buyer and the income statement to a seller, and both are correct.
Every entry below is defined the way it gets used by someone selling options rather than buying them, with SPX as the reference contract. Terms that have a full page on this site get a short definition and a link rather than a duplicate explanation — the strategy library and the Greeks pages go far deeper than a glossary should.
Contract Basics
Premium
The price of an option contract, quoted per share. A quote of 17.00 costs $1,700 for one standard contract because of the 100-share multiplier. To a buyer it’s the amount at risk; to a seller it’s the credit collected up front and the maximum possible profit on the position.
Strike Price
The price at which the contract settles if it finishes in the money. For an SPX put struck at 7,450, everything below 7,450 at expiration has value and everything above it expires worthless. Strike selection is the single biggest lever a seller has over win rate.
Expiration and DTE
DTE means days to expiration — the number of calendar days left until the contract settles. A contract with 30 DTE expires in a month; one with 0 DTE expires today. DTE drives almost everything else: how fast time decay runs, how violent gamma becomes, how much a position moves on a given index point.
0DTE
An option on its expiration day, with zero days to expiration remaining. On SPX these are SPXW contracts, listed daily and settled in cash at the 4:00 PM ET close. The whole life cycle of the trade fits inside one session. See 0DTE Options Trading for the mechanics in full.
Exercise
Converting an option into its settlement value. European-style contracts like SPX can only be exercised at expiration; American-style contracts like SPY can be exercised any trading day. The distinction decides whether a short position can be closed out against your wishes mid-trade — see European vs American Style Options .
Assignment
What happens to the seller when a buyer exercises. On an American-style equity option it means shares change hands at the strike, potentially before expiration. SPX sellers face no early assignment at all, because a European contract cannot be exercised before its final day.
Cash Settlement
Settling in cash rather than shares. An in-the-money SPX contract produces a debit or credit equal to the intrinsic difference times $100, and the position simply disappears. Nothing carries overnight, and no stock position appears in the account. Compare with physical settlement .
Multiplier and Notional
The multiplier converts a quoted price into dollars — $100 per point for SPX, SPY and XSP alike. Notional is the exposure that controls: one SPX contract with the index at 7,500 carries $750,000 of notional. This is why position sizing on SPX has little to do with the premium collected.
Moneyness and Value
Moneyness
Where the strike sits relative to the current index level. In the money (ITM) has intrinsic value, at the money (ATM) sits at roughly the current price, and out of the money (OTM) has none. Sellers spend most of their time OTM, collecting the premium on contracts they expect to expire worthless.
Intrinsic Value
The part of an option’s price you would keep if it settled right now. A 7,450 put with SPX at 7,420 has 30 points of intrinsic value. It cannot go below zero, and it does not decay — time decay only ever eats the other component.
Extrinsic Value
Everything in the price that is not intrinsic — the probability premium the buyer pays for what might still happen. An ATM 0DTE option is 100% extrinsic at entry. This is the entire inventory a premium seller has to sell, and the reason theta matters more to sellers than to buyers.
Breakeven
The index level where the position turns from loss to profit at expiration. For a short put it is the strike minus the credit collected; sell the 7,450 put for 17.00 and you keep money down to 7,433. Every structure has one or two — the formulas are collected in max loss and max profit .
Pin Risk
The uncertainty that comes from the underlying finishing at or very near your short strike. On cash-settled SPX there is no share-delivery surprise, but the final settlement print still decides whether a strike that looked safe all afternoon finishes a point in the money. Wings exist partly for this.
The Greeks in One Line Each
Delta
The rate an option’s price changes per one-point move in the underlying, and a rough proxy for the probability of finishing in the money. A 0.25-delta short strike gains or loses about $25 per SPX point and finishes ITM roughly a quarter of the time. Full detail: Delta .
Gamma
The rate delta itself changes as the underlying moves. Gamma is small with weeks left and enormous in the last hours of an expiration day, which is why a 0DTE position that looked comfortable at noon can be a different trade by 3:00 PM. Full detail: Gamma .
Theta
The dollars a position gains or loses per day from the passage of time alone. Theta is negative for every long option and positive for every short one — the seller’s income line. It accelerates as expiration approaches and is largest at the money. Full detail: Theta .
Vega
Sensitivity to a one-point change in implied volatility. Short premium is short vega: a volatility spike raises the price of the contracts you sold and shows an unrealized loss even when the index has not moved against you at all. Full detail: Vega .
Rho
Sensitivity to a one-percentage-point change in interest rates. Rho is the Greek that matters least to a 0DTE seller — over a few hours the rate component is immaterial — and matters most on long-dated contracts like LEAPS. Full detail: Rho .
Volatility
Implied Volatility (IV)
The volatility the market is currently pricing into a contract, expressed as an annualized percentage. It is derived from the option’s price rather than from history — an output of what people are paying, not a forecast. Higher IV means richer premium for a seller, and a wider range the market expects.
IV Rank
Where current IV sits between its lowest and highest readings over the past year, on a 0–100 scale. An IV rank of 80 means IV is near the top of its own annual range. It answers “is premium rich for this product”, which a raw IV number never does.
IV Percentile
The share of trading days in the past year when IV closed below today’s level. IV percentile of 70 means IV was lower on 70% of days. It differs from IV rank by being insensitive to a single extreme spike distorting the range.
IV Crush
The rapid collapse in implied volatility once an anticipated event passes. Options priced for uncertainty lose extrinsic value the moment the uncertainty resolves, regardless of direction. Index sellers see a mild version around scheduled macro events; the violent version belongs to single-stock earnings.
Expected Move
The range the options market is pricing for a given period, approximated by the at-the-money straddle price. If the ATM straddle on SPX is trading at 45 points, the market is implying roughly a ±45-point session. Useful as a sanity check on how far OTM a short strike really is.
VIX
An index derived from SPX option prices that expresses the market’s implied volatility for the next 30 days. It is a thermometer for option premium rather than a directional signal — VIX rises when SPX falls because demand for protection rises, not because a decline has been predicted.
Volatility Skew
The tendency for equally-distant OTM puts to carry higher implied volatility than OTM calls. Downside protection is in structurally higher demand, so it costs more. Skew is why a put spread and a call spread placed at the same delta rarely bring in the same credit.
Structures Sellers Use
Credit Spread
Any structure entered for a net credit: you sell one option and buy a cheaper, further-out one for protection. The credit is the maximum profit, and the distance between strikes minus that credit is the maximum loss. The bull put spread and bear call spread are the two building blocks.
Debit Spread
The mirror image — entered for a net payment, profiting only if the underlying moves the right way. Maximum loss is the debit paid, maximum profit is the spread width minus that debit. Buyers use these; sellers mostly meet them as the other side of the trade.
Vertical Spread
Two options of the same type and same expiration, different strikes. Every credit and debit spread named above is a vertical. “Vertical” refers to reading down a single expiration column in an options chain, as opposed to a calendar, which reads across expirations.
Wings
The long, further-OTM options in a four-legged structure such as an iron condor . Wings cost money and reduce the credit, and they are what converts an undefined-risk position into a defined-risk one. Wing width sets the maximum loss directly.
Short Strike
The option you sold — the strike that defines where the position starts losing money. In a defined-risk spread it is the strike being protected by a wing further out. Delta on the short strike is the usual shorthand for how aggressive a position is.
Naked (Uncovered)
A short option with no long option or stock position behind it. A naked short call carries theoretically unlimited risk, which is why brokers require the highest approval level and the largest margin for it. See Naked Short Call .
Defined vs Undefined Risk
Defined risk means the worst case is a fixed, known number set by the structure — every spread and condor qualifies. Undefined risk means the loss has no structural cap, as with naked short options. The distinction matters more than win rate: one bad day can only end an account in the second category.
Rolling
Closing an existing position and opening a similar one further out in time, further out in strike, or both, usually as a single order. Rolling for a credit genuinely improves the position; rolling for a debit to avoid taking a loss is a loss deferred, not an adjustment.
Execution and the Order Book
Bid-Ask Spread
The gap between the highest price a buyer will pay and the lowest a seller will accept. It is a real cost paid on entry and again on exit, and it widens with illiquid strikes and fast markets. Four-legged structures pay it four times over — see slippage .
Mid Price
The midpoint between bid and ask, and the price most limit orders are aimed at first. A fill at the mid is the reasonable expectation on liquid SPX strikes; anything materially worse than the mid on a routine entry is a cost worth measuring rather than accepting.
Slippage
The difference between the price you expected and the price you actually got. It includes crossing the spread, moving with a fast market, and the partial fills that come with multi-leg orders. Small per trade, decisive across hundreds of them.
Open Interest
The number of contracts in that strike currently outstanding — positions opened and not yet closed. Unlike volume, it carries over between sessions. High open interest usually means tighter quotes, because market makers are active where inventory already sits.
Volume
Contracts traded in that strike during the current session, reset to zero each morning. Volume shows today’s activity; open interest shows accumulated positioning. A strike with heavy volume and thin open interest is being traded and closed intraday, which is normal for 0DTE.
Buying Power Reduction
The capital a broker sets aside while a position is open. For a defined-risk spread it is usually the maximum loss; for naked positions it is a formula-based margin requirement that can be many times the credit collected. It, not the premium, determines how many positions an account can hold — and it draws on cash available to trade , not settled cash.
Fill
The execution of an order. A complete fill takes the whole quantity at the stated price; a partial fill takes some of it, which on a multi-leg order can leave a structure temporarily incomplete and unbalanced. Limit orders control price, not certainty of a fill.
Frequently Asked Questions
What is a credit spread in options?
A credit spread is a two-leg position entered for a net credit: you sell one option and buy a further-out option of the same type and expiration as protection. The credit received is the maximum profit; the strike width minus that credit is the maximum loss.
What does DTE mean in options?
DTE means days to expiration — how many calendar days remain until the contract settles. 0DTE means the option expires today. DTE governs how quickly time decay runs and how sharply the position reacts to price moves near expiration.
What is the difference between intrinsic and extrinsic value?
Intrinsic value is the amount an option is already in the money, which never decays. Extrinsic value is everything else — the probability premium for what might still happen — and it decays to zero by expiration. Sellers are selling extrinsic value.
What is open interest in options?
Open interest is the number of contracts at a given strike that are currently open and not yet closed. It accumulates across sessions, unlike volume, which resets daily. Higher open interest generally means tighter bid-ask spreads at that strike.
Related Articles
- Introduction to Options Trading — the concepts behind these terms, in the order a new trader needs them.
- Option Selling and Its Advantages — why the premium-seller’s definitions differ from the textbook ones.
- The Options Greeks — delta, gamma, theta, vega and rho at full depth, one page each.
- Options Payoff Diagrams — every structure named in the Structures section, drawn.
This content is for educational purposes only. Options trading involves significant risk of loss. Always trade within your risk tolerance.