The standard Russian language reduces the vowel to [ɪ], but yakanye dialects ⟨я⟩ undergo no reduction unlike other instances of the /a/ phoneme (represented with the letter ⟨а⟩).

The letter ѧ, known as little jus (yus) (Bulgarian: малка носовка, Russian: юс малый) originally stood for a front nasal vowel, conventionally transcribed as ę.

In Serbia, [ɛ̃] became [e] at a very early period and the letter ѧ ceased to be used, being replaced by e. In Bulgaria the situation is complicated by the fact that dialects differ and that there were different orthographic systems in use, but broadly speaking [ɛ̃] became [ɛ] in most positions, but in some circumstances it merged with [ǫ], particularly in inflexional endings, e.g. the third person plural ending of the present tense of certain verbs such as правѧтъ (Modern Bulgarian правят).

This reflects the practice of earlier scribes and was further codified by the Muscovite printers of the seventeenth century (and is continued in modern Church Slavonic).

In nineteenth-century Bulgaria, both Old Cyrillic and civil scripts were used for printing, with я in the latter corresponding to ѧ in the former, and there were various attempts to standardise the orthography, of which some, such as the Plovdiv school exemplified by Nayden Gerov, were more conservative, essentially preserving the Middle Bulgarian distribution of the letter, others attempted to rationalise spelling on more phonetic principles, and one project in 1893 proposed abolishing the letter я altogether.

[2] By the early twentieth century, under Russian influence, я came to be used for /ja/ (which is not a reflex of ę in Bulgarian), retaining its use for /jɐ/ but was no longer used for other purposes; this is its function today.

Although [æ] is a distinctive pronunciation of ⟨я⟩ in Russian, the letter is almost never used to transcribe that sound, unlike the use of ⟨ю⟩ to approximate close front and central rounded vowels.