Option chains

Definition

An option chain is the full grid of listed option contracts on one underlying: every expiration date crossed with every strike, each carrying a call and a put with its own bid, ask, last, volume, and open interest. The chain is the raw data surface from which all options analytics (pillar 3) are computed.

How it works / structure

• Axes: expirations (weekly, monthly, quarterly, LEAPS) × strikes (exchange-set intervals that densify near the money); liquid underlyings list thousands of individual contracts.
• Per-contract fields: bid/ask (the tradable market), last sale, volume (today’s contracts traded), open interest (contracts outstanding, updated overnight), and derived fields — implied volatility per contract, greeks per contract.
• Derived structures: the IV surface (strike × expiry → IV), skew read across strikes (opt-volatility-skew), term structure read across expiries (opt-term-structure), at-the-money straddle pricing (opt-expected-move).
• Data hygiene: quotes update continuously but open interest is previous-day; single-print “last” prices on illiquid contracts can be hours stale — analytics read mid-quotes with liquidity filters.

When it applies

Reading a chain precedes any options trade or options-informed thesis: strategy legs are selected from it, expected moves are priced off it, and flow/positioning measures aggregate over it. Chain breadth and quote quality are the first liquidity screen for whether an options strategy is executable at all.

Risk profile & failure modes

• Stale-data traps: last-sale prices and unrefreshed quotes on thin strikes misprice analytics; mid-of-market on a 40%-wide quote is not a price.
• Open-interest misreading: OI lags a day and does not reveal direction — high OI is not “bullish positioning” without further evidence (indicator-options-flow covers the traps).
• Strike-listing artifacts: new strikes appear as price moves; historical chain comparisons must account for listing changes.
• Aggregation errors: summing volume across calls and puts, or across moneyness, produces measures with very different meanings — definitions must be exact.

Evidence & limits

Chain structure and fields are exchange/clearing specifications (OCC, Cboe), not hypotheses. The informational value of chain-derived measures is assessed per measure in pillar 3 and indicator-options-flow; this entry makes no predictive claims.

Falsifiable-thesis examples

Illustrations only, not signals:

• “X’s chain will list weekly expirations continuously for the next 6 months” — falsified if a listed weekly cycle is dropped.
• “Total open interest across X’s chain, at N contracts today, will exceed 1.5N within 90 days” — falsified if the published OI never reaches that level.

Cross-references

• Contract mechanics: instrument-option-contract, ms-expiration-exercise-assignment, ms-contract-specs
• Analytics computed from the chain: opt-implied-volatility, opt-iv-rank-percentile, opt-volatility-skew, opt-term-structure, opt-put-call-ratio, opt-expected-move, indicator-options-flow
• Execution quality: ms-bid-ask-spread, ms-liquidity