Chi (call)

Chi is the call used to claim an opponent's discarded tile in order to complete a chow, a run of three consecutive tiles in one suit. When you declare chi, you take the discard, lay your chow face-up (rotating the claimed tile to show where it came from), and your hand becomes open. The call exists across Japanese, Chinese, and Hong Kong mahjong, though it is forbidden in some regional styles such as Sichuan bloody rules.

The defining restriction of chi is direction: you may only chi from the player seated immediately to your left, that is, the player whose turn comes just before yours. This is unlike pon and kan, which can claim a discard from any of the three opponents. If two players want the same discard, a pon or ron also takes priority over a chi, since those represent stronger claims.

Calling chi speeds up your hand by letting you grab a sequence tile instead of waiting to draw it, but it carries costs. Opening your hand disqualifies riichi in Japanese rules and removes many closed-hand yaku, so a chi should usually only be made when your hand already has a yaku such as tanyao or a yakuhai in progress. It also reveals information about your hand to the table.

For example, suppose you hold 5m-6m and the player to your left discards 7m. You may call chi to form the open chow 5m-6m-7m, choosing whether to display it as completing the left, middle, or right of your run. The same 7m discarded by the player across from you cannot be chi'd; you would have to wait and draw a 4m or 7m yourself.