Yōon or Youon (拗音) is a feature of the Japanese language in which a mora is formed with an added y sound.
Yōon is represented in kana using a kana ending in i, such as き (ki), plus a smaller-than-usual version of one of the three y kana, ya, yu or yo. For example kyō, "today", is written きょう, using a small version of the yo kana, よ. Contrast this with kiyō, "skillful", which is written きよう, with a full-sized yo kana. In the past, in historical kana usage, yōon was not distinguished with the smaller kana, and had to be guessed by context.
Most of the words which now use yōon were originally derived from Chinese. The ancient version of Japanese did not have any yōon sounds. It is theorised that yōon developed because of the influence of the Chinese words.
| ゃ ya | ゅ yu | ょ yo | |
|---|---|---|---|
| k | キャ kya | キュ kyu | キョ kyo |
| sh | シャ sha | シュ shu | ショ sho |
| ch | チャ cha | チュ chu | チョ cho |
| n | ニャ nya | ニュ nyu | ニョ nyo |
| h | ヒャ hya | ヒュ hyu | ヒョ hyo |
| m | ミャ mya | ミュ myu | ミョ myo |
| r | リャ rya | リュ ryu | リョ ryo |
| dakuten | |||
| g | ギャ gya | ギュ gyu | ギョ gyo |
| j | ジャ ja | ジュ ju | ジョ jo |
| b | ビャ bya | ビュ byu | ビョ byo |
| p | ピャ pya | ピュ pyu | ピョ pyo |