// GLOSSARY

Yes / No side

The two sides of a binary market. Yes and no prices are complements — they sum to $1 at fair value — so buying no at 58¢ is economically the mirror of selling yes at 42¢. Each side has its own book presentation, and liquidity can differ between them.

Every binary market has two tradable sides. Because exactly one pays $1 at settlement, fair prices are complements: if yes is worth 42¢, no is worth 58¢.

Worked example

Yes is quoted 41¢ bid / 43¢ ask. The implied no market is 57¢ bid / 59¢ ask (complement and swap the sides: the yes ask caps what no can be worth). If you can actually buy yes at 43¢ and buy no at 55¢ somewhere — total 98¢ for a guaranteed $1 payout — that's a 2¢ arbitrage before fees, the single-market version of the cross-venue trades in Kalshi–Polymarket arbitrage.

Venue mechanics

Kalshi presents both yes and no as buyable sides of one market, quoted in cents. Polymarket implements them as two distinct ERC-1155 outcome tokens, each with its own token ID and book on the CLOB. Functionally equivalent, but your code must handle both shapes — and check both sides' books: the same exposure is sometimes cheaper expressed as "buy no" than "sell yes," especially after fees.