Ukeire

Ukeire 「受け入れ」, or tile acceptance, refers to the number of tiles that you could draw to reduce shanten count (i.e. get closer to tenpai). This is typically considered when a hand is 2-shanten or below, since 3-shanten and higher hands often have a very high ukeire.

Occasionally, tile acceptance can also include tiles that could upgrade the hand (i.e. a tile that increases the hand's ukeire).