The hard sign (⟨ъ⟩) is commonly used as a "silent back vowel" that separates a succeeding "soft vowel" (я, ё, ю, е, but not и) from a previous consonant, invoking implicit iotation of the vowel with a different /j/ glide. In modern language, it is mainly used for separating a prefix ending with a hard consonant from the following root. Its initial pronunciation, lost by 1400 at the latest, represented that of a very short middle schwa-like sound, /ŭ/ but likely pronounced [ə] or [ɯ]. Until the reform in 1918, no written word could end in a consonant: those that end in a ("hard") consonant in modern orthography then had a final ъ.
While ⟨и⟩ also represents a soft vowel, root-initial /i/ following a hard consonant is usually pronounced as [ɨ]. The letter is typically spelled ⟨ы⟩ (the hard counterpart to ⟨и⟩) unless this vowel is at the beginning of a word, in which case it remains ⟨и⟩. The alternation between the two letters (but not the sounds) can be recognized with the pair без и́мени ('without a name,' which is pronounced [bʲɪz ˈɨmʲɪnʲɪ]) and безымя́нный ('nameless,' which is pronounced [bʲɪzɨˈmʲænːɨj]). However, this spelling convention, is not applied with specific loaned prefixes like in the word панислами́зм – [ˌpanɨsɫɐˈmʲizm], 'Pan-Islamism') and compound (multi-root) words (e.g., госизме́на – [ˌɡosɨˈzmʲenə], 'high treason').
The soft sign (⟨ь⟩) in most positions is used like a "silent front vowel." The sign indicates that the preceding consonant is palatalized (except for always-hard ш, ц, ж) and the following vowel is iotated (including ьо in loans). The sign is essential as palatalization is phonemic in the Russian language. For instance, брат [brat] ('brother') contrasts with брать [bratʲ] ('to take'). The original pronunciation of the soft sign, lost by 1400 at the latest, represented that of a very short fronted reduced vowel /ĭ/ but likely pronounced [jɪ] or [ɪ]. There are still some remnants of this ancient reading in modern Russian, e.g., in co-existing versions of the same name, written and read differently, like Мария and Марья (Mary).
When applied after stem-final always-hard (ш, ж, but not ц) or always-soft (щ, ч, but not й) consonants, the soft sign does not alter pronunciation, but has grammatical significance:
- the feminine marker for singular nouns in the accusative and nominative; e.g., тушь ('India ink,' feminine) cf. туш ('flourish after a toast,' masculine) – both pronounced [tuʂ];
- the infinitives of some verbs (with -чь ending);
- the imperative mood for some verbs;
- some adverbs and particles;
- the second person for non-past verbs (with ending -шь).
The vowels ⟨ю, ё, е, и, я⟩ indicate a preceding palatalized consonant and except for ⟨и⟩ are iotated (pronounced with a preceding /j/) when written at the beginning of a word or following another vowel (original ⟨и⟩ was iotated until the nineteenth century). The IPA vowels indicated are a guideline only and sometimes are realized as different sounds, especially when unstressed. However, ⟨е⟩ may also be used in words of foreign origin without palatalization (/e/), and ⟨я⟩ is frequently realized as [æ] between soft consonants, like in мяч ("toy ball").
⟨ы⟩ is an old Proto-Slavic close central vowel, believed to have been preserved better in modern Russian than in any other Slavic languages. It was initially nasalized in certain positions: камы [ˈkamɨ̃]; камень [ˈkamʲɪnʲ] ("rock"). The development of its written form can be seen below:
⟨ъ⟩ + ⟨і⟩ → ⟨ꙑ⟩ → ⟨ы⟩.
⟨э⟩ was introduced to the language in 1708 to distinguish the non-palatalizing/non-iotated /e/ from the palatalizing/iotated one. The primary usage had been ⟨е⟩ for the uniotated /e/, ⟨ѣ⟩ or ⟨ѥ⟩ for the iotated. However, ⟨ѥ⟩ had dropped out of use by the sixteenth century. In native Russian words, ⟨э⟩ can be found only in compound words (e.g., поэтому "therefore" = по + этому) or at the beginnings of words. In words that are borrowed from foreign languages in which iotated /e/ is not common or does not exist (like English, for instance), ⟨э⟩ is typically written at the beginning of words as well as after vowels except ⟨и⟩ (e.g., поэт, poet), and ⟨е⟩ after ⟨и⟩ and consonants. However, the pronunciation can be considered inconsistent. A lot of words ending in ⟨е⟩ and many words where ⟨е⟩ follows ⟨с⟩, ⟨д⟩, ⟨т⟩, ⟨н⟩, ⟨з⟩, or ⟨р⟩ are pronounced with /e/ without palatalization or iotation. For instance, проект (proekt— "project") (in the indicated example, the spelling is etymological, but the pronunciation is counter etymological). However, a lot of other words are pronounced with /ʲe/: дебют (dyebyut— "debut"), секта (syekta— "sect"). Proper names are normally not concerned by the rule (Пэмела — "Pamela," Мао Цзэдун — "Mao Zedong," Сэм — "Sam"). The use of ⟨э⟩ after consonants is common in English, as well as East Asian names with the sounds /ɛər/ and /æ/. Some exemptions to this rule are names like Шепард ("Shepard") or Джек ("Jack"), since both ⟨е⟩ and ⟨э⟩ are always following hard (non-palatalized) consonants in cases of ше ("she"), це ("tse"), and же ("zhe"), yet in writing ⟨е⟩ usually prevails.
⟨ё⟩, introduced by Karamzin in 1797 and established officially in 1943 by the Soviet Ministry of Education, marks a /jo/ sound that developed from stressed /Je/. The written letter ⟨ё⟩ is optional. The letter is officially correct to write ⟨e⟩ for both /Je/ and /jo/. However, it is not considered necessary. Despite several attempts in the twentieth century aimed to mandate the use of ⟨ё⟩ have remained.
Letters in disuse by 1750
⟨ѱ⟩ and ⟨ѯ⟩ derived from Greek letters are pronounced as psi and xi. Both were used etymologically in secular writing until the eighteenth century, and more consistently to the present day in Church Slavonic.
⟨ѡ⟩ represents the Greek letter omega, which is identical in pronunciation to ⟨о⟩. The letter was common in secular writing until the eighteenth century. Today it can be met in Church Slavonic, mostly used to distinguish inflexional forms otherwise written identically.
⟨ѕ⟩ corresponded to a more archaic /dz/ pronunciation, already absent in East Slavic at the beginning of the historical period, but kept by tradition in certain words until the eighteenth century in secular writing, and in Macedonian and Church Slavonic to the present day.
The uses ⟨ѧ⟩ and ⟨ѫ⟩, and letters were originally used to stand for nasalized vowels /ẽ/ and /õ/. Still, they later became irrelevant for East Slavic phonology at the beginning of the historical period. The letters ⟨ѩ⟩ and ⟨ѭ⟩ had mostly vanished by the twelfth century. The ⟨ѫ⟩ continued to be used, etymologically, until the sixteenth century. After that, it was reduced to being a dominical letter in the Paschal tables. The seventeenth-century usage of ⟨ѧ⟩ and ⟨ѫ⟩ exists in contemporary Church Slavonic and the sounds (but not the letters) in Polish.
The letter ⟨ѧ⟩ was adapted to represent the iotated /ja/ ⟨я⟩ in the end or middle of a word; the modern letter ⟨я⟩ represents an adaptation of its cursive form of the seventeenth century, blessed by the typographical reform of 1708.
Until 1708, the iotated /ja/ looked like ⟨ꙗ⟩ and was used at the beginning of a word. This distinction between ⟨ꙗ⟩ and ⟨ѧ survives in Church Slavonic.
Even though it is usually stated that the letters labeled "fallen into disuse by the eighteenth century" in the table above were eliminated in the typographical reform of 1708, the reality is somewhat more complex. The letters were originally omitted from the sample alphabet, printed in a western-style serif font, presented in Peter's proclamation, along with the letters ⟨и⟩, ⟨ф⟩, and ⟨з⟩ (replaced by ⟨ѕ⟩), and (the letter ⟨й⟩ was also removed). Still, they were reinstated except ⟨ѡ⟩ and ⟨ѱ⟩ under pressure from the Russian Orthodox Church in a later variant of the modern typeface (1710). Nonetheless, since 1735 the Russian Academy of Sciences began to use fonts without ⟨ѯ⟩, ⟨ѕ⟩ and ⟨ѵ⟩. However, ⟨ѵ⟩ was sometimes used repeatedly since 1758.
Letters eliminated in 1918
I - Decimal - Identical in pronunciation to ⟨и⟩, was used immediately in front of other vowels and the ⟨й⟩ ("Short I") (for example, ⟨міръ⟩ [mʲir] ('world') and in the word ⟨патріархъ⟩ [pətrʲɪˈarx], 'patriarch').
ѣ - Yat - Initially had a distinct sound, but by the middle of the eighteenth century had become identical in pronunciation to ⟨е⟩ in the standard language. After its elimination in 1918, it remained as a political symbol of the old orthography.
ѳ - Fita - From the Greek theta, pronounced exactly like ⟨ф⟩ but was used etymologically (for instance, ⟨Ѳёдоръ⟩ "Theodore" became ⟨Фёдор⟩ "Fyodor").