Why can one Japanese sentence use several kinds of characters?

A Japanese sentence can combine kanji, hiragana and katakana. These are not three different spoken languages inside one sentence. They are writing systems used together to represent Japanese. Their usual jobs differ, which helps readers recognize words and grammatical information.

Kanji are characters with historical origins in Chinese writing. They often represent meaningful word parts, but they are not simply pictures that anyone can understand. A character can have more than one reading. The kanji 山, for example, can write the word yama, meaning mountain. Hiragana can also write that spoken word as やま. The two hiragana signs represent its sound units rather than separately meaning mountain.

Hiragana frequently writes grammatical endings and particles, as well as words written without kanji. Katakana represents a corresponding set of sound units and is often used for borrowed words, sound effects or emphasis. Kana are commonly called syllabaries; more precisely, their basic units correspond to Japanese morae, units of spoken timing. A unit such as ん is a reminder that these do not always match English-style syllables.

The diagram compares 山 with やま and ヤマ. All can be read yama in this example, although their normal uses and effects differ. The comparison does not mean every kanji has exactly one reading or every word can be substituted freely without changing style. A writing system is a set of conventions for a language, and several kinds of convention can work together on one page.