When kanji were imported from China in about the 5th Century AD, they came with their original Chinese pronunciation, but they were also allocated the current Japanese pronunciation for the meaning of the character. Then, because kanji were imported at different times and from different regions in China, some kanji accumulated more than one Chinese pronunciation. That is why now, most kanji have at least two, but sometimes more than two pronunciations.
The Chinese pronunciation is called the ‘on’ reading, or on-yomi, and the Japanese pronunciation is called the ‘kun’ reading, or kun-yomi. As a general rule, the ‘kun’ reading is used when the kanji is written as a single-unit kanji and the ‘on’ reading is used when the kanji is a part of a compound (when two or more kanji characters make up one word). In order to help distinguish ‘on’ from ‘kun’ in kanji learning resources, the ‘on’ reading is often presented in katakana while the ‘kun’ reading is usually presented in hiragana. This makes sense since katakana is used for foreign words.
Some examples of ‘on’ and ‘kun’ readings are:
|Meaning||‘Kun ’ reading||‘On ’ reading in compound|
|mountain||山 yama||富士山 Fujisan (Mt Fuji)|
|water||水 mizu||水曜日suiyōbi (Wednesday)|
|flower||花 hana||花びん kabin (vase)|