Plain-English definitions of the gamma-exposure and dealer-positioning terms used across HermesGEX — from zero gamma and call walls to charm and vanna.
Gamma Exposure (GEX) measures how much options dealers must buy or sell to stay delta-hedged as the underlying price moves.
Gamma Exposure aggregates the gamma of every option on a chain into a single curve that shows where dealer hedging will absorb or amplify price moves. Positive total GEX implies dealers buy dips and sell rips (volatility dampened); negative total GEX implies they sell weakness and chase strength (volatility amplified).
Also known as: GEX · gamma exposure · options gamma
Learn more:Guide: GEX explainedDocs: What is GEX
Net GEX is the sum of call gamma minus put gamma across all strikes, summarizing the market-wide dealer gamma sign.
Net GEX collapses the whole profile into one number: a large positive value points to a pinning, mean-reverting tape, while a negative value warns of trend-prone, high-volatility conditions. Traders watch when Net GEX crosses zero as a regime change signal.
Also known as: net gamma exposure · total gex
Zero Gamma is the price level where net dealer gamma flips from positive to negative, marking the boundary between volatility suppression and amplification.
Above the zero-gamma (flip) level dealers are typically long gamma and dampen moves; below it they are short gamma and accelerate them. Because behavior changes sign there, the flip level often acts as a pivotal intraday support/resistance.
Also known as: gamma flip · flip level · zero gamma level · gamma flip point
Learn more:Guide: Zero gammaDocs: How to read the map
The Call Wall is the strike with the largest call gamma, which tends to act as resistance / a price magnet.
Heavy dealer call gamma concentrated at one strike forces sustained selling as price approaches, which frequently caps rallies into expiration. A break above the call wall can flip prior resistance into a fast-move zone.
Also known as: call resistance · gamma resistance
Learn more:Docs: How to read the map
The Put Wall is the strike with the largest put gamma, which tends to act as support / a downside floor.
Concentrated dealer put gamma drives buying as price falls toward the strike, which often cushions sell-offs. Losing the put wall removes that support and can open the door to accelerated downside.
Also known as: put support · gamma support
Learn more:Docs: How to read the map
In a long-gamma regime dealers hedge against the move (buy dips, sell rips), which suppresses realized volatility.
Long-gamma conditions usually produce range-bound, mean-reverting price action with shallow pullbacks. They typically occur when the underlying trades above the zero-gamma level.
Also known as: positive gamma · long gamma
Learn more:Guide: Long vs short gamma
In a short-gamma regime dealers hedge with the move (sell weakness, buy strength), which amplifies realized volatility.
Short-gamma conditions favor trends, gaps, and momentum cascades because hedging adds fuel to the prevailing direction. They typically occur when the underlying trades below the zero-gamma level.
Also known as: negative gamma · short gamma
Learn more:Guide: Long vs short gamma
Dealer positioning describes the net options inventory market makers hold and the hedging flows it forces them to execute.
Because dealers must hedge their books, their aggregate gamma, vanna, and charm exposure becomes a predictable, mechanical source of buying and selling. Reading that positioning lets traders anticipate where flows will support or pressure price.
Also known as: market maker positioning · dealer hedging
Learn more:Docs: Dealers & hedging
Charm is the rate at which an option’s delta changes as time passes, driving predictable dealer hedging into the close and expiration.
As expiration nears, charm pulls option deltas toward 0 or 1, forcing dealers to mechanically adjust hedges — often producing the late-day drift and end-of-week flows traders track. Charm effects are strongest around large open-interest strikes.
Also known as: charm · delta decay · DdeltaDtime
Learn more:Feature: Greek Flow
Vanna measures how an option’s delta shifts when implied volatility changes, linking volatility moves to dealer hedging flows.
When implied volatility falls (e.g. a “vol crush”), vanna forces dealers to buy the underlying, fueling the classic rallies seen after fear subsides. Rising volatility works in reverse, adding selling pressure.
Also known as: vanna · DdeltaDvol
Learn more:Feature: Greek Flow
HVL marks the price area where dealer gamma turns most negative, flagging the zone where volatility is likely to expand fastest.
Trading into the HVL warns that hedging flows will accelerate rather than absorb moves, so breaks through it often coincide with the day’s sharpest swings. It complements the zero-gamma level as a volatility road map.
Also known as: high volatility level · hvl
0DTE options expire the same trading day, so their gamma is extreme and dealer hedging can dominate intraday price action.
Because 0DTE gamma spikes near the money, even small spot moves trigger large hedging flows that create pinning into key strikes or violent breakouts when those strikes fail. This makes intraday GEX especially important for 0DTE-heavy markets.
Also known as: zero days to expiration · 0 DTE · same-day options
Learn more:Guide: 0DTE gamma pinning
Delta Exposure (DEX) is the aggregate delta dealers must hedge across the options chain, showing the directional pressure their hedging adds to the underlying.
While GEX measures hedging of the rate-of-change in delta, DEX measures the directional inventory itself. Sharp shifts in DEX often precede or confirm large directional flows, which is why traders watch DEX spikes to locate where size is entering the market.
Also known as: delta exposure · DEX · aggregate delta
Learn more:Feature: Greek Flow
A gamma squeeze is a self-reinforcing rally where dealer hedging of short call gamma forces dealers to keep buying the underlying, accelerating the move.
When traders buy large amounts of calls, dealers short those calls and must buy the underlying to stay hedged; as price rises their required hedge grows, creating a feedback loop. Gamma squeezes fade once the driving options are sold, expire, or delta saturates near 1.
Also known as: gamma squeeze · call gamma squeeze
Pinning is the tendency of price to gravitate toward a high-gamma strike into expiration, as dealer hedging repeatedly pushes it back toward that level.
Near expiration, concentrated gamma at a strike makes dealer hedging buy below it and sell above it, magnetizing price to that level (the “pin”). Pin risk is the resulting uncertainty for option holders about whether they finish in or out of the money.
Also known as: pinning · pin risk · gamma pin · price pin
Learn more:Guide: 0DTE gamma pinning
OPEX is an options-expiration date — especially monthly and quarterly expirations — when large gamma rolls off and dealer hedging can shift the volatility regime.
As expiring options stop requiring hedges, the gamma that was pinning or cushioning price disappears, often “unclenching” the market and freeing larger moves in the days after. Monthly and quarterly (triple / quad witching) expirations carry the largest open interest and the strongest effects.
Also known as: OPEX · options expiration · triple witching · quad witching
Learn more:Playbook: OPEX
Implied volatility (IV) is the market’s expectation of future price movement priced into an option, and a key input that drives vanna and dealer hedging.
IV rises with demand for options (often during fear) and falls when that demand fades. Because changing IV moves option deltas via vanna, shifts in IV translate directly into dealer hedging flows, linking the volatility surface to spot price action.
Also known as: implied volatility · IV
Volatility skew is the difference in implied volatility across strikes, typically with downside puts priced richer than upside calls.
Skew reflects how the market prices crash risk: a steep put skew means investors pay up for downside protection, shaping dealer inventory and the vanna / charm flows that follow. Tracking skew changes helps anticipate where hedging pressure will build.
Also known as: skew · vol skew · volatility smile
Max pain is the strike where the largest total value of options expires worthless, often acting as a gravitational price target into expiration.
Because that strike inflicts the greatest aggregate loss on option buyers (and the greatest gain for sellers), price sometimes drifts toward it as dealer hedging and pinning align. Max pain is a heuristic, strongest near expiration in high-open-interest names.
Also known as: max pain · maximum pain · pin strike
Open interest (OI) is the total number of outstanding option contracts at a strike, showing where positioning — and therefore dealer gamma — is concentrated.
High-OI strikes are where hedging flows cluster, so they frequently become the call walls, put walls, and pin levels traders track. Watching OI build-up reveals where the next gamma-driven support, resistance, or magnet is forming.
Also known as: open interest · OI
The put/call ratio compares put activity to call activity — a sentiment gauge where high readings signal bearish or hedging demand and low readings signal bullish positioning.
Beyond raw sentiment, the mix of puts vs. calls shapes dealer gamma and vanna: heavy put buying loads dealers with positioning that drives different hedging than a call-heavy tape. Extreme readings are often interpreted as contrarian signals.
Also known as: put/call ratio · put call ratio · PCR
Delta hedging is how dealers neutralize directional risk by buying or selling the underlying to offset the delta of their options book — the mechanical flow GEX analysis predicts.
Because dealers continuously rebalance to stay delta-neutral, their trades are forced and predictable rather than discretionary. Gamma, vanna, and charm all describe how that required hedge changes, which is why dealer delta hedging is the engine behind GEX-based levels.
Also known as: delta hedging · delta-neutral hedging
Learn more:Docs: Dealers & hedging
HermesGEX turns these concepts into real-time gamma maps for index, equity and crypto options.