The ratio of [the size of the bet a player is facing] in relation to [the size of the pot]. For example, a player facing a half-pot bet can call, risking 0.5 to win 1 (the pot) and 0.5 (their opponent's bet), and therefore is being laid odds of 3:1. They need 1 / (3+1) = 25% to break even on a call. A common misconception is that the player facing the bet needs 25% equity, when in fact they need to win 25% of the value of the pot. If that player could face future bets then they need to estimate their expected value rather than relying on raw equity.