If a player discards a tile and this tile is the tile you need to go Mah Jongg, you can pick up the tile if it is to make an identical pair, a Chow or a Pung, and go Mah Jongg.
There are circumstances when you are not allowed to pick up a discarded tile and go Mah Jongg - this occurs when two or more players want to pick up the same discarded tile. See Precedences section for more information. See Precedences for more information.
See also Rules.