Tanyao (断幺九) is a yaku, consisting of tile groups using numbered tiles 2-8 of any of the three main suits. Conversely, this yaku must lack the terminal tiles (1 and 9) as well as any honor tiles. Among the yaku, this is one of the more easier to attain. In turn, it is also a cheap yaku. In addition, this yaku may be subject to rule variation of allowing or disallowing its count when opened.
Tiles numbers 2-8 are designated as "simples". Its converse, the 1 and 9 tiles plus honor tiles, is grouped as the terminals and honors. So, in order to form a hand with tanyao, players simply discard the terminal and honor tiles. Given the range of the simple tiles, the number of tiles available to form this yaku is a wide range. This availability makes this yaku a particularly fast one to develop. It is even faster, when used in open fashion. Although, some rules may vary, which disallows the use of tanyao for open hands.
The speed of the hand's development justifies the value of the hand at 1-han. This speedy play is associated with cheap value.
If red fives are used, it is easier to turn tanyao into a high-scoring hand.