Prediction Market Glossary 2026: 50 Essential Terms Explained

Engaging in prediction market trading requires familiarity with terminology rooted in finance, mathematics, and distributed ledger systems. This comprehensive glossary presents 64 vital concepts that every prediction market participant ought to grasp — encompassing execution mechanics, portfolio protection strategies, decentralised infrastructure, and probabilistic forecasting frameworks.

Core Trading Terms

Ask (Offer): The minimum price threshold at which a seller agrees to part with shares. When you acquire at prevailing market rates, you transact at the ask price.
Bid: The maximum price a purchaser will commit to for acquiring shares. When you dispose of holdings at prevailing market rates, you obtain the bid price.
Bid-Ask Spread: The gap separating the best ask from the best bid. Narrower spreads indicate deeper liquidity and correspondingly reduced transaction expenses.
CLOB (Central Limit Order Book): The order-matching infrastructure deployed by Polymarket and PolyGram. It pairs pending purchase and sale orders according to price precedence and temporal sequence.
Conditional Token: The blockchain-based manifestation of a YES or NO entitlement within a prediction market. These assets reside within smart contracts deployed on Polygon.
Fill Price: The precise price at which your transaction was completed. This may diverge from the initially quoted price should market conditions shift between submission and settlement.
FOK (Fill or Kill): An instruction type requiring instantaneous full execution or automatic cancellation. Partial satisfaction is not permitted.
Liquidity: The capacity to transact shares swiftly without materially moving the price. Markets characterised by substantial volume and compressed spreads demonstrate superior liquidity.
Market Order: An instruction to transact at the most competitive price currently obtainable. Execution occurs immediately, though at the prevailing market rate.
Limit Order: An instruction to transact exclusively at a designated price or more favourably. The instruction persists in the order book until a counterparty is found or the instruction is withdrawn.
Open Interest: The aggregate monetary value of all unresolved active positions within a market. Elevated open interest signals stronger participation and greater depth.
Slippage: The variance between anticipated execution price and the actual price received, typically stemming from insufficient depth at the desired price level.

Probability & Statistics Terms

Brier Score: A metric quantifying forecast precision. Smaller values indicate superior performance. Computation involves the mean squared deviation between your estimated likelihood and the realised outcome (either 0 or 1).
Calibration: An assessment of alignment between your probability judgements and subsequent empirical outcomes. Excellent calibration manifests when assertions made with 70% confidence materialise approximately 70% of the time.
Expected Value (EV): The probable outcome when considering all scenarios weighted by their respective likelihoods. Positive EV indicates a wager with profitable characteristics across repeated instances.
Kelly Criterion: A mathematical framework governing ideal stake allocation: f = (bp - q) / b, where b represents net odds, p denotes your assessed likelihood, and q equals 1-p.
Superforecaster: An individual exhibiting consistently superior calibration across numerous forecasts, conforming to the classification established in Philip Tetlock's scholarly work.

Blockchain & Settlement Terms

Polygon: The secondary-layer blockchain infrastructure underpinning Polymarket and PolyGram operations. It facilitates transactions costing fractions of a cent with confirmation within approximately 2 seconds.
USDC (USD Coin): The dollar-pegged digital currency employed for prediction market settlement. One USDC maintains parity with one USD, with issuance managed by Circle and collateralisation via US government securities.
Smart Contract: Autonomous executable protocols residing on the blockchain that custody prediction market capital and orchestrate automatic disbursements upon market conclusion.
Oracle: An authoritative information conduit transmitting factual outcomes to blockchain protocols. Polymarket leverages UMA's optimistic oracle mechanism for market determination.
Gas: The compensation remitted to Polygon network operators for validating transactions. On Polygon, this typically remains beneath $0.01 per operation.

Market Types

Binary Market: A market structure permitting precisely two competing outcomes (YES/NO). This represents the predominant configuration for prediction markets.
Categorical Market: A market structure accommodating multiple distinct outcomes (for instance, "Which candidate will secure the Republican nomination in 2028?").
Scalar Market: A market where compensation adjusts proportionally to the outcome magnitude (for example, "At what level will BTC trade on December 31?").
Conditional Market: A market whose determination hinges upon a prerequisite event transpiring. The market becomes void should the prerequisite fail to materialise.

FAQ

Where can I learn more prediction market terminology?: PolyGram's API documentation provides thorough treatment of technical vocabulary. Polymarket's support resources address consumer-oriented definitions.
What is the difference between a prediction market and a futures contract?: Futures contracts maintain a dynamic price reflecting an underlying commodity or instrument. Prediction markets deliver a fixed $0 or $1 settlement contingent upon whether an event transpires.
What does it mean when a market is "resolved YES"?: The outcome materialised, and YES positions yield $1 apiece. NO positions yield nothing. Payout execution occurs mechanically through blockchain protocols.