Definition
An exposure is a completed set laid face up on top of your rack after calling a discard, visible to every player for the rest of the hand.
Exposures are information: three of a number narrows your possible hands sharply, and opponents will stop feeding you. They also make any joker inside them available for exchange.
Read the full guide: Calling and Exposing in American Mahjong: When, How, and When Not To.
See it on real tiles: the coach reads any hand and names its direction, free, at the free read. Members get the coach on call for their own games.
More terms: Pung, Kong, Quint, Pair, Charleston, Blind pass, Courtesy pass, Joker.