Plain-English definitions of the prediction-market terms used across PredTerminal, covering Polymarket and Kalshi. Built for traders and for AI assistants that need a clear, citable source.
Maintained by PredTerminal, tracking Polymarket and Kalshi in real time.
- Prediction market
- A market where you trade on the outcome of a future event, such as an election, a Fed rate decision, or a game. Prices move with the crowd’s estimate of how likely the outcome is.
- Market (event)
- A single question that resolves to a definite outcome, for example "Will X happen by a given date?" Each market trades YES and NO shares.
- Outcome (YES/NO shares)
- A share that pays $1 if its outcome happens and $0 if it does not. Buying YES at $0.60 means the market is pricing a 60% chance of that outcome.
- Implied probability
- A market price read as a percentage chance. A YES share trading at $0.42 implies a 42% probability that the event happens.
- Resolution
- The settlement of a market once the real-world event is decided. Winning shares pay $1 and losing shares pay $0.
- Resolution source (oracle)
- The authority that determines a market’s official outcome. Polymarket uses the decentralized UMA optimistic oracle; Kalshi resolves as a regulated exchange.
- Whale bet
- A large prediction-market trade. PredTerminal marks bets of $10,000 and up, because that size usually means someone is confident or knows something, rather than noise.
- Sharp money (smart money)
- Bets placed by historically accurate traders. PredTerminal tags wallets with strong track records as SHARP so you can see when proven traders move.
- Insider signal
- A pattern such as contrarian bets, coordinated entries, or unknown wallets buying aggressively that can indicate non-public information ahead of an event.
- Arbitrage between sites
- When the same question costs less on one betting site than another, buying the cheaper side and selling the dearer side can lock in a profit after fees, whichever way the event goes.
- Order book
- The live list of buy and sell orders for an outcome at each price. It shows where demand and supply sit right now.
- Liquidity
- How much money is available to trade at or near the current price. Deep liquidity means a large bet moves the price less.
- Spread
- The gap between the best buy price (bid) and the best sell price (ask) for an outcome. A tight spread means an efficient, liquid market.
- Volume
- The total value traded in a market. Higher volume usually means more conviction and a more reliable, tighter price.
- Open interest
- The total value of outstanding positions in a market that have not yet been closed or resolved.
- Polymarket
- A large decentralized prediction-market platform where outcomes settle on-chain in USDC and disputes are resolved through the UMA oracle.
- Kalshi
- A US-regulated prediction-market exchange, overseen by the CFTC, where event contracts settle in dollars.
- Mark price (mid)
- The midpoint between the best bid and the best ask. It is used as a fair-value estimate of the current implied probability.
- Top trader (leaderboard)
- A ranking of wallets by profit, ROI, win rate, or volume, used to find and follow proven prediction-market traders.
- Kelly criterion
- A formula for working out how much to stake, based on your advantage and the odds, so your money grows over time without you betting so big you go broke.
- Resolution date (expiry)
- The date a market is expected to settle, once the outcome of the underlying event becomes known.
- Value (your advantage)
- The difference between the chance the market price implies and your own estimate of the real chance. A bet has value when you think the market has the price wrong in your favour.