In Japanese, nouns and stems of adjectives and verbs are almost all written in Chinese characters called kanji. Adverbs are also fairly frequently written in kanji as well. This means that you will need to learn Chinese characters to be able to read essentially almost all the words in the language.
It is said that some 50,000 kanji exist, however, many kanji are not necessarily used in daily life. The Japanese Ministry of Education designated 1,945 characters as Jooyoo Kanji, which are the most frequently used characters.
Kanji have two distinct readings – On and Kun. Many use different readings for completely different words. On top of that, many have multiple On and Kun readings to further complicate which one to use to pronounce a word. In general, the On is used in compounds, words with more than one kanji in them, and the Kun is used when the kanji is by itself.
On’yomi, Chinese Reading or simply the On Reading
On is basically ‘sound’ in Japanese and represents the fact the On reading is the adaption of the Chinese reading of the kanji in question. These primarily occur in compound words (ie – more than one kanji in the word)
Kun’yomi, Japanese Reading or simply the Kun Reading
In comparison, the Kun reading is simply the Japanese reading of the meaning of the Chinese kanji when it was first introduced.
If you would like to learn Kanji click here