Kana ligature
In the Japanese writing system, kana ligatures are ligatures in the kana writing system, both hiragana and katakana. Kana such as and are not kana ligatures, but polysyllabic kana. Most of such ligatures and polysyllabic kanas became obsolete.
Hardly any kana ligatures or polysyllabic kanas are represented in standard character encodings.
History
These characters were widely used until a spelling reform decreed that each sound would be represented by one character. In January 1900, the Kana Investigation Committee passed a resolution to "limit the number of homophone kana characters to one each" and aimed to abolish hentaigana, iteration marks, long-vowel marks,, the characters ゐ/ヰ and ゑ/ヱ, as well as the ligatures and the polysyllabic kanas.Kana ligatures such as,, etc., were actively used in Japan during the Edo and Meiji periods. These ligatures were sometimes placed together along with the hiragana and katakana syllabaries in Japanese school textbooks. Nowadays, these ligatures are obsolete and are not taught at schools anymore.