Reference

SPX and 0DTE options glossary

Plain definitions of the dealer-positioning terms used across the desk: gamma exposure, the gamma flip, call and put walls, options flow, implied volatility and the contract identifiers behind every study.

0DTE options Options expiring the same trading day.: 0DTE means zero days to expiration: the contract expires at the end of the current session. SPX lists an expiry every weekday, so 0DTE trading is available daily. Premium decays fastest here and dealer hedging is concentrated near spot, which is why gamma levels matter far more intraday than they do for longer-dated contracts.
Gamma exposure (GEX) How much dealers must hedge as price moves.: Gamma exposure aggregates the gamma of open options positions to estimate how much underlying dealers must buy or sell for each point the index moves. Positive net gamma implies hedging that trades against the move and dampens ranges; negative net gamma implies hedging that trades with the move and widens them.
Gamma flip The price where net dealer gamma changes sign.: The gamma flip is the index level at which aggregate dealer gamma crosses zero. Above it dealer hedging is typically stabilising, so pullbacks are absorbed; below it hedging is typically destabilising, so moves extend. Traders watch it as a regime line rather than a support or resistance level.
Call wall The strike with the heaviest call gamma above spot.: The call wall is the strike above the current price carrying the largest concentration of call gamma or open interest. Hedging flows around it often slow advances, so it is used as an upside magnet or stall zone rather than a guaranteed ceiling.
Put wall The strike with the heaviest put gamma below spot.: The put wall is the strike below the current price carrying the largest concentration of put gamma or open interest. It often marks where downside hedging demand clusters; losing it tends to open a faster, less-cushioned move lower.
Dealer hedging Market-maker trading in the underlying to stay neutral.: When market makers sell options they take on directional risk and offset it by trading the underlying. Because that hedge must be adjusted continuously as price, time and volatility change, the aggregate hedge becomes a mechanical flow — the reason options positioning can shape index behaviour intraday.
Options flow The live stream of executed options trades.: Options flow is the record of trades as they print: contract, size, premium, whether it hit the bid or the ask, and how it compares to existing open interest. Large, aggressive, out-of-the-money prints are watched because they express conviction rather than routine hedging.
Market tide Net premium tilt between calls and puts.: Market tide compares net call premium against net put premium across the session to show which side money is paying up for. A persistent tilt is read as directional pressure; a flattening tide is read as pressure being unwound.
Implied volatility and IV crush Priced-in movement, and its collapse after an event.: Implied volatility is the movement the option's price implies over its remaining life. IV crush is the sharp drop in implied volatility once an expected event passes — the reason a directionally correct option can still lose value after the catalyst prints.
Open interest Contracts still outstanding at a strike.: Open interest counts the contracts that remain open at a given strike and expiry. Rising open interest with rising volume indicates new positioning; rising volume with falling open interest indicates positions being closed. Concentrations of open interest are what build gamma walls.
OSI contract symbol The standard code identifying one option contract.: The OSI symbol packs root, expiry date, side and strike into a single identifier, for example SPXW 251219C06000000. The desk validates it so a contract referenced in a study, a screenshot or an archive entry always resolves to exactly one contract.
Multiplier expansion A contract's premium expanding to a multiple of its base.: Multiplier expansion describes a session in which a contract's premium travels from a low base to several times that value. The desk documents each case with the ignition time, the peak, and the flow, gamma and volatility conditions present while it expanded — as research, never as a forecast.
Breakeven and payoff Where a position starts making money at expiry.: Breakeven is the underlying price at which a position's expiry value equals what was paid or received; the payoff curve maps value across a range of prices. The desk's scenario lab plots both against current gamma levels so the required move can be compared with the levels that would have to break.

Definitions are educational reference material, not trading advice or a recommendation.

Back to overview

SPX and 0DTE options glossary

0DTE options

Gamma exposure (GEX)

Gamma flip

Call wall

Put wall

Dealer hedging

Options flow

Market tide

Implied volatility and IV crush

Open interest

OSI contract symbol

Multiplier expansion

Breakeven and payoff