Tenhou (天和) is a yakuman attained by completing a hand with the 14 starting tiles that one draws during one's dealer turn. The dealer's initial hand may use any pattern, as long as 13 tiles constitute a tenpai hand, and the 14th tile counts as menzen tsumo.
Formation
Tenhou hands need no action from the player, other than recognition of a complete hand with the 14 dealt tiles and the declaration of a winning hand. Failure to do so may result in a lost opportunity to score this rare yakuman.