Yus

Big Yus was a part of the Bulgarian alphabet until 1945. However, by then, in the eastern dialects, the back nasal was pronounced the same way as ъ [ɤ]. Because the language is based mainly on them, the western pronunciations were deemed unliterary, and the letter was gone.

There were some Bulgarian and Macedonian dialects spoken around Thessaloniki and Kastoria in northern Greece (Kostur dialect, Solun dialect) that still preserve a nasal pronunciation e.g. [ˈkɤ̃de ˈɡrẽdeʃ ˈmilo ˈt͡ʃẽdo] (Къде гредеш, мило чедо?; "Where are you going, dear child?"), which could be spelled pre-reform as "Кѫдѣ грѧдешъ, мило чѧдо?" with big and little yus.

On a visit to Razlog, in Bulgaria's Pirin Macedonia, in 1955, the Russian dialectologist Samuil Bernstein noticed that the nasal pronunciation of words like [ˈrɤ̃ka] (hand), [ˈt͡ʃẽdo] (child) could still be heard from some of the older women of the village. To the younger people, the pronunciation was completely alien; they would think that the old ladies were speaking Modern Greek.[2]

In Russia, the little Yus came to be pronounced as an iotated /ja/ (я) in the middle or at the end of a word and therefore came to represent that sound also elsewhere; the modern letter я is an adaptation of its cursive form of the 17th century, enshrined by the typographical reform of 1708. (That is also why я in Russian often corresponds to nasalized ę in Polish; cf. Russian пять; Polish pięć.)

In Polish, which is a Slavic language written in the Latin alphabet, the letter Ę ę has the phonetic value of little Yus, and Ą ą has that of big Yus. The iotated forms are written ię, ią, ję, ją in Polish. However, the phonemes written ę and ą are not directly descended from those represented by little and big yus but developed after the original nasals merged in Polish and then diverged again. (Kashubian, the closest language to Polish, uses the letter ã instead of ę.)

Little and big yuses can also be found in the Romanian Cyrillic alphabet, used until 1862. Little Yus was used for /ja/ and big Yus for /ɨ/. Now Romanian uses the Latin alphabet and /ɨ/ is written Îî or Ââ.

Little yus in Slovak language alphabet has been substituted by a (desať, načať), e (plesať), iotified ia (žiadať, kliatba, mesiac), ie (bdieť) and ä in several cases (pamäť, päť, svätý). Big yus is transliterated and pronounced as u, or accented ú (budeš, muž, mučeník, ruka, navyknúť, pristúpiť, púť, usnúť). Iotified, and closed iotified form of little yus occur as ja (e.g. jazyk, svoja, javiť, jasle).