What Is an Exposure in American Mahjong?

An exposure is a completed tile group placed faceup on top of or beside a player's rack. It usually appears after the player calls another person's discard to complete a legal pung, kong, quint, or other exposable group.

How an ordinary exposure is created

A tile is discarded

Another player places a tile in the discard area and names it.
You call promptly

You announce the call before play advances beyond the accepted point of finality.
You display the complete group

The called tile and matching tiles from your rack are placed faceup together.
You discard

After completing the exposure, you discard one tile and play continues from you.

What an exposure does and does not do

It reveals structure

Opponents can see the exact group, suit, number, honors, and any jokers used.

It does not identify the full hand

Several card lines may contain the same exposed group, especially early in the game.

It commits the tiles

The exposed group cannot be freely rearranged into an unrelated hand later.

Exposure safeguards

Confirm the chosen card line is open, not concealed.
Expose the exact printed group size.
Use only matching natural tiles and legal jokers.
Do not expose a pair merely to improve the rack.
Do not take a discard without completing a legal group.
Recheck the line before making a second exposure.

Exposure trades flexibility for speed

Calling a useful discard can move a hand closer to completion, but the visible group narrows future choices and gives opponents defensive information. Strong calls improve a realistic hand enough to justify that cost.