Soft sign

The soft sign is normally written after a consonant and indicates its softening (palatalization). Less commonly, the soft sign just has a grammatically determined usage with no phonetic meaning (like Russian: туш 'fanfare' and тушь 'India ink', both pronounced [tuʂ] but different in grammatical gender and declension). In East Slavic languages and some other Slavic languages (such as Bulgarian), there are some consonants that do not have phonetically different palatalized forms but corresponding letters still admit the affixing soft sign.

The Serbian Cyrillic alphabet has had no soft sign as a distinct letter since the mid-19th century: palatalization is represented by special consonant letters instead of the sign (some of these letters, such as ⟨Њ⟩ or ⟨Љ⟩, were designed as ligatures with the grapheme of the soft sign). The modern Macedonian alphabet, based on the Serbian Cyrillic variant, has had no soft sign since its creation, in 1944.

Between a consonant and a vowel, the soft sign bears also a function of "iotation sign": in Russian, vowels after the soft sign are iotated (compare Russian льют [lʲjut] '(they) pour/cast' and лют [lʲut] '(he is) fierce'). The feature, quite consistent with Russian orthography, promulgated a confusion between palatalization and iotation, especially because ⟨ь⟩ usually precedes so-called soft vowels. Combinations ⟨ья⟩ (ya), ⟨ье⟩ (ye), ⟨ьё⟩ (yo) and ⟨ью⟩ (yu) give iotated vowels, like corresponding vowel letters in isolation (and word-initially), and unlike its use immediately after a consonant letter in which palatalization can occur but not iotation. In those cases, ⟨ь⟩ may be considered as a sign indicating that a vowel after it is pronounced separately from the previous consonant, but that is the case neither for ⟨ьи⟩ (yi) nor for ⟨ьо⟩ (yo), because these vowels are not iotated in isolation. The latter case, though, is rarely used in Russian (only in loanwords such as ⟨бульон⟩) and can be seen as a replacement of phonetically identical ⟨ьё⟩, which gets rid of an "inconvenient" letter ⟨ё⟩. In Ukrainian and Bulgarian, the spelling ⟨ьо⟩ indicates palatalization, not iotation.

⟨ъ⟩, an "unpalatalization sign", also denotes iotation, as in the case of ⟨ъя⟩, ⟨ъе⟩, ⟨ъё⟩ and ⟨ъю⟩ in Russian.

Similarly, the soft sign may denote iotation in Belarusian and Ukrainian, but it is not used so extensively as in Russian. Ukrainian uses a quite different repertoire of vowel letters from those of Russian and Belarusian, and iotation is usually expressed by an apostrophe in Ukrainian. Still the soft sign is used in Ukrainian if the sound followed by an iotated vowel is palatized.

Among Slavic languages, the soft sign has the most limited use in Bulgarian: since 1945, the only possible position is one between consonants and ⟨о⟩ (such as in names Жельо, Кръстьо, and Гьончо).

In Slavistic transcription, Ь and Ъ are used to denote Proto-Slavic extra-short sounds /ĭ/ and /ŭ/ respectively (slověnьskъ adj. ‘slavonic’), like Old Slavonic orthography.

It is used in Janalif, the first Soviet-made Latin alphabet, to denote ɯ; its Cyrillic equivalent is ы.

The soft sign does not occur after vowels in Slavic languages, but the ⟨аь⟩ digraph for [æ] or [a] was introduced to some non-Slavic Cyrillic-based alphabets such as Chechen, Ingush and various Dagestanian languages such as Tabasaran. Similarly, the ⟨оь⟩ digraph was introduced for [œ] or [ø], and ⟨уь⟩ for [y], plus iotated forms such as ⟨юь⟩ and ⟨яь⟩ as required. This use of ь is similar to a trailing e as used in, for example, German, when umlauts are unavailable (cf. Goethe).

There were proposals to use the same for Turkic languages,[1] as a replacement to Cyrillic Schwa (Ә) for [ə] or /æ/. Unlike Schwa, which is not represented in many Cyrillic character repertoires such as Windows-1251, both ⟨а⟩ and ⟨ь⟩ are readily available as letters of the basic modern Russian alphabet.

Along with the hard sign and the palochka, the soft sign is a modifier letter in Caucasian languages and Crimean Tatar. Its function is to create a new sound, such as i.e. гь, which is used in Avar, Archi, and Tabasaran to denote /h/.