During the alphabet reforms of Peter I, all diacritic marks were removed from the Russian writing system, but shortly after his death, in 1735, the distinction between ⟨И⟩ and ⟨Й⟩ was restored.

Because ⟨Й⟩ was considered to be a vowel and not a consonant, it was not required to take a hard sign when it came at the end of a word in pre-reform orthography.

In Russian, it appears predominantly in diphthongs like /ij/ in широкий (shirokiy 'wide'), /aj/ in край (kray 'end', 'krai'), /ej/ in долей (doley 'portion'), /oj/ in горой (goroy 'mountain'), and /uj/ in буйство (buystvo 'rage').

In Kazakh, the letter is used to represent a short ɪ sound (e.g. берейік (tr.

In Serbo-Croatian and Macedonian, the Cyrillic letter Јe is used to represent the same sound.