Kanji (漢字) are used to write the following:
nouns, including Japanese names
stems of adjectives and verbs.
Hiragana (平仮名) are used to write the following:
okurigana (送り仮名)―inflectional endings for adjectives and verbs
joshi (助詞)―grammatical particles
words that lack a kanji, where the kanji is obscure, difficult to typeset, or is considered too difficult (as in children's books)
furigana (振り仮名)―phonetic renderings of kanji. Furigana may aid children or nonnative speakers or clarify nonstandard, rare, or ambiguous readings.
Katakana (片仮名) are used to write the following:
foreign words and names
commonly used animals, plants or objects whose kanji are rare, such as tokage (lizard), bara (rose) and rōsoku (candle)
onomatopoeia
emphasis, much like italicisation in European languages
technical and scientific terms, such as plant, animal, and mineral names
.