Calligraphy is based on a typographic writing system, referring to Kanji, which is an ideogram, and in the case of Japanese calligraphy also on syllabaries (currently there are two: Hiragana and Katakana, although in the past there were more). There is also an exceptional syllabary in the Chinese language called Nushu 女書 ("female writing"), although it is not used in classical calligraphy. However, due to its unique character, Nushu can sometimes be included in the group of calligraphy styles.