Calling chow
A chow is a run of three consecutive tiles in one suit. You may claim a discard to complete a chow only if it was discarded by the player immediately before you (on your left). Say "chow" (or "chi" in Japanese play), take the tile and lay the completed run face up, then discard.
American Mah Jongg does not allow chows at all: runs in American hands are made from single tiles, and singles can never be claimed for an exposure.
Calling pung
You may claim a discarded tile from any player to complete a pung if you hold two of the same tile. Call "pung" (or "pon"), take the tile, expose the three, and discard. Play then continues from your right, which means any players between the discarder and you lose their turns.
Because of this turn-skipping effect, punging can be used tactically — to deny a turn to a dealer close to winning, for example.
Calling kong
If you hold three of a tile and another player discards the fourth, you may claim it for an exposed kong. You may also declare a concealed kong when you draw the fourth yourself, or add a drawn fourth tile to an exposed pung. After any kong you draw a replacement tile from the dead wall to keep the right count.
Kongs usually score more than pungs, and in Japanese play each kong reveals a new dora indicator — good for you, but also for everyone else.
The cost of calling
Every call reveals information and, in many styles, reduces your hand's value or restricts which scoring elements you can use. Japanese riichi players cannot declare riichi after calling, and several of the most valuable hands must be fully concealed. Calling also commits you: an exposed set can never be changed.
A useful beginner rule is to call when it moves you meaningfully closer to a hand that still scores, and to hold back when it merely tidies a hand that will be worth little.
