Courtesy: Russian exemption letter
The Russian alphabet contains 10 vowel letters. They are grouped into soft and hard vowels. The soft vowels, ⟨е, ё, и, ю, я⟩, either indicate a preceding palatalized consonant, or (with the exception of ⟨и⟩) are iotated (pronounced with a preceding /j/) in all other cases. The IPA vowels shown are a guideline only and sometimes are realized as different sounds, particularly when unstressed. However, ⟨е⟩ may be used in words of foreign origin without palatalization (/e/), and ⟨я⟩ is often realized as [æ] between soft consonants, such as in мяч (‘toy ball’).
⟨ы⟩ is an old Proto-Slavic close central vowel, thought to have been preserved better in modern Russian than in other Slavic languages. It was originally nasalized in certain positions: Old Russian камы [ˈkamɨ̃]; Modern Russian камень [ˈkamʲɪnʲ] (‘rock’). Its written form developed as follows: ⟨ъ⟩ + ⟨і⟩ → ⟨ꙑ⟩ → ⟨ы⟩.
⟨э⟩ was introduced in 1708 to distinguish the non-iotated/non-palatalizing /e/ from the iotated/palatalizing one. The original usage had been ⟨е⟩ for the uniotated /e/, ⟨ѥ⟩ or ⟨ѣ⟩ for the iotated, but ⟨ѥ⟩ had dropped out of use by the sixteenth century. In native Russian words, ⟨э⟩ is found only at the beginnings of a few words э́тот/э́та/э́то ‘this (is) (m./f./n.)’, э́ти ‘these’, э́кий ‘what a’, э́дак/э́так ‘that way’, э́дакий/э́такий ‘sort of’, and interjections like эй ‘hey’) or in compound words (e.g. поэ́тому ‘therefore’ = по + этому, where этому is the dative case of этот). In words that come from foreign languages in which iotated /e/ is uncommon or nonexistent (such as English), ⟨э⟩ is usually written in the beginning of words and after vowels except ⟨и⟩ (e.g. поэ́т, ‘poet’), and ⟨е⟩ after ⟨и⟩ and consonants. However, the pronunciation is inconsistent. Many of these borrowed words, especially monosyllables, words ending in ⟨е⟩ and many words where ⟨е⟩ follows ⟨т⟩, ⟨д⟩, ⟨н⟩, ⟨с⟩, ⟨з⟩ or ⟨р⟩, are pronounced with /e/ without palatalization or iotation: секс (seks — ‘sex’), моде́ль (model’ — ‘model’), кафе́ (kafe — ‘café’), прое́кт (proekt — ‘project’; here, the spelling is etymological: German Projekt was adopted from Latin proiectum, so the word is spelled with ⟨е⟩ to reflect the original /je/ and not with ⟨э⟩ as usual after vowels; but the pronunciation is counter-etymological: a hypercorrection that has become standard). But many other words are pronounced with /ʲe/: се́кта (syekta — ‘sect’), дебю́т (dyebyut — ‘debut’). Proper names are sometimes written with ⟨э⟩ after consonants: Сэм — ‘Sam’, Пэме́ла — ‘Pamela’, Мэ́ри — ‘Mary’, Ма́о Цзэду́н — ‘Mao Zedong’; the use of ⟨э⟩ after consonants is common in East Asian names and in English names with the sounds /æ/ and /ɛər/, with some exceptions such as Джек (‘Jack’) and Ше́ннон (‘Shannon’), since both ⟨э⟩ and ⟨е⟩, in cases of же (“zhe”), ше (“she”) and це (“tse”), follow consonants that are always hard (non-palatalized), yet ⟨е⟩ usually prevails in writing. However, English names with the sounds /ɛ/, /ə/ (if spelled ⟨e⟩ in English), and /eɪ/ after consonants are normally spelled with ⟨е⟩ in Russian: Бе́тти — ‘Betty’, Пи́тер — ‘Peter’, Лейк-Плэ́сид — ‘Lake Placid’. Pronunciation mostly remains unpalatalized, so Пи́тер [ˈpʲitɛr] — Russian rendering of the English name ‘Peter’ is pronounced differently from Пи́тер [ˈpʲitʲɪr] — colloquial Russian name of Saint Petersburg.
⟨ё⟩, introduced by Karamzin in 1797 and made official in 1943 by the Soviet Ministry of Education, marks a /jo/ sound that historically developed from stressed /je/. The written letter ⟨ё⟩ is optional; it is formally correct to write ⟨e⟩ for both /je/ and /jo/. None of the several attempts in the twentieth century to mandate the use of ⟨ё⟩ have stuck.
Hard sign
The hard sign (⟨ъ⟩) acts like a “silent back vowel” that separates a succeeding “soft vowel” (⟨е, ё, ю, я⟩, but not ⟨и⟩) from a preceding consonant, invoking implicit iotation of the vowel with a distinct /j/ glide. Today it is used mostly to separate a prefix ending with a hard consonant from the following root. Its original pronunciation, lost by 1400 at the latest, was that of a very short middle schwa-like sound, likely pronounced [ə] or [ɯ]. Until the 1918 reform, 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⟩ is also a soft vowel, root-initial /i/ following a hard consonant is typically pronounced as [ɨ]. This is normally spelled ⟨ы⟩ (the hard counterpart to ⟨и⟩) unless this vowel occurs at the beginning of a word, in which case it remains ⟨и⟩. An alternation between the two letters (but not the sounds) can be seen with the pair без и́мени (‘without name’, which is pronounced [bʲɪz ˈɨmʲɪnʲɪ]) and безымя́нный (‘nameless’, which is pronounced [bʲɪzɨˈmʲænːɨj]). This spelling convention, however, is not applied with certain loaned prefixes such as in the word панислами́зм – [ˌpanɨsɫɐˈmʲizm], ‘Pan-Islamism’) and compound (multi-root) words (e.g. госизме́на – [ˌɡosɨˈzmʲenə], ‘high treason’).