What is "hentaigana"

n. (context Japanese English) a variant form of a hiragana or katakana character.

In the Japanese writing system, are obsolete or nonstandard hiragana. They include both stylistic variants of current hiragana and distinct alternative hiragana characters. Today, with a few exceptions, there is only one hiragana for each of the fifty consonant–vowel sequences (moras) in Japanese. However, traditionally there were generally several more-or-less interchangeable hiragana for each. A 1900 script reform ordained that only one selected character be used for each mora, with the rest deemed hentaigana. Although not normally used in publication, hentaigana are still used in shop signs and brand names to create a traditional or antiquated air.

Hiragana originate in man'yōgana, a system where kanji were used to write sounds without regard to their meaning. There was more than one kanji that could be used equivalently for each syllable (at the time, a syllable was a mora). Over time the man'yōgana was reduced to a cursive form, the hiragana. Many hentaigana derive from different kanji from the ones for the now-standard hiragana, but some are the result of different styles of cursive writing. As hentaigana have derived from man'yōgana, there are hundreds of different hentaigana used to represent only 90 morae of the Japanese language.

On the other hand, katakana do not have hentaigana. Katakana's choices of man'yōgana segments had stabilized early on and established – with few exceptions – an unambiguous phonemic orthography (one symbol per sound) long before the 1900 script regularization.

Hentaigana are not included in Unicode, though there is a proposal to encode them.