On’yomi and kun’yomi, and how to tell which reading a word uses
Most kanji have a Chinese-derived on reading and a native Japanese kun reading. Here’s where they come from, a rule of thumb for which one a word uses, and the exceptions worth knowing.
One of the first shocks of learning kanji is finding out that most of them can be read in more than one way. 山 is yama on its own, but san in 富士山 (Fujisan). 水 is mizu, but sui in 水曜日 (suiyōbi, Wednesday). It feels arbitrary, but there’s a pattern, and once you see it you’ll guess right far more often than not.
Where two readings come from
Kanji came to Japan from China. Japanese borrowed the characters along with an approximation of their Chinese pronunciation. That’s the on’yomi (音読み), the “sound reading”.
Japanese already had its own words, though. So each character was also given the native word with the same meaning. That’s the kun’yomi (訓読み), the “meaning reading”. 山 was borrowed as san, and the Japanese word for mountain, yama, was attached to it too.
Some kanji were borrowed more than once, from different periods and regions of China, so they have more than one on reading. 行 is kō in 銀行 (ginkō, bank), gyō in 行列 (gyōretsu, queue) and an in 行脚 (angya, pilgrimage). And a few kanji have a whole family of readings. 生 is sei in 先生 (sensei), shō in 一生 (isshō, a lifetime), i in 生きる (ikiru, to live), u in 生まれる (umareru, to be born) and nama in 生ビール (nama bīru, draught beer).
The rule of thumb
- A kanji on its own, or followed by hiragana, usually takes its kun reading. 山 yama, 食べる taberu, 大きい ōkii.
- Two or more kanji together usually take their on readings. 食事 shokuji (meal), 大学 daigaku (university), 山脈 sanmyaku (mountain range).
That alone gets you a long way.
The exceptions worth knowing
- Kun + kun compounds. Some compounds are native Japanese all the way through: 手紙 tegami (letter), 花火 hanabi (fireworks), 名前 namae (name).
- Mixed compounds. A few mix the two. When the on reading comes first it’s called 重箱読み (jūbako-yomi), after 重箱 jūbako itself, as in 毎朝 maiasa (every morning). The other way round is 湯桶読み (yutō-yomi), named after 湯桶 yutō, as in 場所 basho (place).
- Special readings. Some words are read as a whole, and the reading doesn’t break down kanji by kanji: 今日 kyō (today), 明日 ashita (tomorrow), 大人 otona (adult). These just have to be learned as words.
Reading a dictionary entry
Dictionaries usually write on readings in katakana and kun readings in hiragana. A dot or a dash marks where the kanji stops and the hiragana ending begins: た.べる means the kanji covers ta, and beru is written in hiragana.
Learn readings through words
The best way to learn readings isn’t a list of every reading a kanji has. It’s a couple of everyday words for each kanji, because the word tells you the reading. There’s more on that in how to learn kanji for the JLPT a few minutes a day.
That’s how Kanji Detective teaches them. You can question a suspect by typing a reading as well as a kanji or a meaning, and once the case closes, the case file lists the kanji’s on and kun readings with romaji, alongside example words that show which reading goes where. The daily case is free, works offline and needs no account.