yotsugana

thumb|right|350px|Different regions distinguish different sets of sounds. Using Nihon-shiki romanization:

are a set of four specific kana, じ, ぢ, ず, づ (in the Nihon-shiki romanization system: zi, di, zu, du), used in the Japanese writing system. They historically represented four distinct voiced morae (syllables) in the Japanese language. However, most dialects, such as Standard Japanese-speakers, have undergone mergers and now pronounce two sounds.