Japanese sentences are usually written using a mix of hiragana, katakana, and kanji. Although it is possible to write a sentence in only hiragana or katakana characters, it is hard for most Japanese people to understand because the kanji symbols represent a concept which the kana do not show. Small kana symbols, however, can be put above kanji to show how it is pronounced (this is called furigana and is used a lot in karaoke).