No full-fledged script for written Japanese existed until the development of man'yōgana (万葉仮名), which appropriated kanji for their phonetic value (derived from their Chinese readings) rather than their semantic value. Man'yōgana was initially used to record poetry, as in the Man'yōshū (万葉集), compiled sometime before 759, whence the writing system derives its name. The modern kana, namely hiragana and katakana, are simplifications and systemizations of man'yōgana.

Due to the large number of words and concepts entering Japan from China which had no native equivalent, many words entered Japanese directly, with a pronunciation similar to the original Chinese. This Chinese-derived reading is known as on'yomi (音読み), and this vocabulary as a whole is referred to as Sino-Japanese in English and kango (漢語) in Japanese. At the same time, native Japanese already had words corresponding to many borrowed kanji. Authors increasingly used kanji to represent these words. This Japanese-derived reading is known as kun'yomi (訓読み). A kanji may have none, one, or several on'yomi and kun'yomi. Okurigana are written after the initial kanji for verbs and adjectives to give inflection and to help disambiguate a particular kanji's reading. The same character may be read several different ways depending on the word. For example, the character 行 is read i as the first syllable of iku (行く, "to go"), okona as the first three syllables of okonau (行う, "to carry out"), gyō in the compound word gyōretsu (行列, "line" or "procession"), kō in the word ginkō (銀行, "bank"), and an in the word andon (行灯, "lantern").

Some linguists have compared the Japanese borrowing of Chinese-derived vocabulary as akin to the influx of Romance vocabulary into English during the Norman conquest of England. Like English, Japanese has many synonyms of differing origin, with words from both Chinese and native Japanese. Sino-Japanese is often considered more formal or literary, just as latinate words in English often mark a higher register.