Cyrillic digraphs

The Cyrillic script family contains many specially treated two-letter combinations, or digraphs, but few of these are used in Slavic languages. In a few alphabets, trigraphs and even the occasional tetragraph or pentagraph are used.

In early Cyrillic, the digraphs ⟨оу⟩ and ⟨оѵ⟩ were used for /u/. As with the equivalent digraph in Greek, they were reduced to a typographic ligature, ⟨ꙋ⟩, and are now written ⟨у⟩. The modern letters ⟨ы⟩ and ⟨ю⟩ started out as digraphs, ⟨ъі⟩ and ⟨іо⟩. In Church Slavonic printing practice, both historical and modern, ⟨оу⟩ (which is considered as a letter from the alphabet's point of view) is mostly treated as two individual characters, but ⟨ы⟩ is a single letter. For example, letter-spacing affects ⟨оу⟩ as if they were two individual letters, and never affects components of ⟨ы⟩. In a context of Old Slavonic language, ⟨шт⟩ is a digraph that can replace a letter ⟨щ⟩ and vice versa.

Modern Slavic languages written in the Cyrillic alphabet make little or no use of digraphs. There are only two true digraphs: ⟨дж⟩ for /d͡ʒ/ and ⟨дз⟩ for /d͡z/ (Belarusian, Bulgarian, Ukrainian). Sometimes these digraphs are even considered as special letters of their respective alphabets. In standard Russian, however, the letters in ⟨дж⟩ and ⟨дз⟩ are always pronounced separately. Digraph-like letter pairs include combinations of consonants with the soft sign ⟨ь⟩ (Serbian/Macedonian letters ⟨љ⟩ and ⟨њ⟩ are derived from ⟨ль⟩ and ⟨нь⟩), and ⟨жж⟩ or ⟨зж⟩ for the uncommon and optional Russian phoneme /ʑː/. Native descriptions of Cyrillic writing system often use the term "digraph" to combinations ⟨ьо⟩ and ⟨йо⟩ (Bulgarian, Ukrainian) as they both correspond to a single letter ⟨ё⟩ of Russian and Belarusian alphabets (⟨ьо⟩ is used for /ʲo/, and ⟨йо⟩ for /jo/).

Cyrillic uses large numbers of digraphs only when used to write non-Slavic languages; in some languages such as Avar, these are completely regular in formation.

Many Caucasian languages use ⟨ә⟩ (Abkhaz), ⟨у⟩ (Kabardian & Adyghe), or ⟨в⟩ (Avar) for labialization, just as many of them, like Russian, use ⟨ь⟩ for palatalization. Since such sequences are decomposable, regular forms will not be listed below. (In Abkhaz, ⟨ә⟩ with sibilants is equivalent to ⟨ьә⟩, for instance ж /ʐ/, жь /ʒ/~/ʐʲ/, жә /ʒʷ/~/ʐʲʷ/, but this is predictable phonetic detail.) Similarly, long vowels written double in some languages, such as ⟨аа⟩ for Abkhaz /aː/ or ⟨аюу⟩ for Kirghiz /ajuː/ "bear", or with glottal stop, as Tajik аъ [aʔ~aː], are not included.