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|Cyrillic letter Yer|
|List of Cyrillic letters|
The letter yer (Ъ, ъ, italics Ъ, ъ) of the Cyrillic script, also spelled jer or er, is known as the hard sign (твёрдый знак [ˈtvʲor.dɨj znak]) in the modern Russian and Rusyn alphabets and as er golyam (ер голям, "big er") in the Bulgarian alphabet. The letter is called back yer in the pre-reform Russian orthography, in Old Russian, and in Old Church Slavonic. Originally the yer denoted an ultra-short or reduced middle rounded vowel. Its companion is the front yer, now known as the soft sign in Russian and as er malək (ер малък, "small er") in Bulgarian (Ь, ь), which was originally also a reduced vowel, more frontal than the ъ, and which is today used to mark the palatalization of consonants in all of the Slavic languages written in the Cyrillic script, except for Serbian and Macedonian, where it is not used although its traces can be seen in the letters њ and љ. The two reduced vowels together are called the yers in Slavic philology.
Original use 
In the Old Church Slavonic language, the yer was a vowel letter, indicating the so-called "reduced vowel": ъ = *[ŭ], ь = *[ĭ] in the conventional transcription. These vowels stemmed from the Proto-Balto-Slavic short */u/ and */i/ (compare Latin angulus and Old Church Slavonic ǫgъlъ. In all West Slavic languages the yer either disappeared or was transformed into /e/ in strong positions, and in South Slavic languages strong yer reflexes differ widely across dialects.
Historical development 
In Common Slavic, the yers were normal short vowels /u/ and /i/. Havlik's law caused yers in certain positions to be pronounced very weakly (perhaps as ultrashort vowels), and to lose the ability to take the word accent. These weak yers were later dropped, while the strong yers evolved into various sounds depending on the individual language.
For determining whether a yer is strong or weak, it is necessary to break the continuous flow of speech into individual words, or prosodic units (phrases which have only a single stressed syllable, and typically include a preposition or other clitic words). The rule for determining which yers are weak and which are strong is as follows:
- A terminal yer is weak.
- A yer which is followed in the next syllable by a non-reduced vowel is weak.
- The yer in the syllable before one with a weak yer is strong.
- The yer in the syllable before one with a strong yer is weak.
In Russian, for example, the yers evolve as follows:
- Strong yers are fully voiced: ь → е (or ë); ъ → о
- weak yers drop entirely, except that the palatalization from a following ь generally remains.
Simply put, in a string of Old Russian syllables each of which has a reduced vowel, the reduced vowels are in modern Russian alternately given full voicing and drop, and the last yer in this sequence will drop. There are some exceptions to this rule, usually considered to be the result of analogy with other words or other inflected forms of the same word, with a different original pattern of reduced vowels. Modern Russian inflection is therefore at times complicated by the so-called "transitive" (lit. беглые [ˈbʲeɡlɨjə] "fugitive" or "fleeting") vowels, which appear and disappear in place of a former yer. For example (OR = Old Russian; R = Russian):
- OR сънъ /ˈsŭ.nŭ/ → R сон [son] "sleep" (nom. sg.)
- OR съна /sŭˈna/ → R сна [sna] "sleep" (gen. sg.)
- OR угълъ /ˈu.ɡŭ.lŭ/ → R угол [ˈu.ɡəl] "corner" (nom. sg.)
- OR угъла /u.ɡŭˈla/ → R угла [ʊˈɡla] "corner" (gen. sg.)
Modern Russian: Hard sign 
In modern Russian the letter "ъ" is called the hard sign (твёрдый знак tvjordyj znak). It has no phonetic value of its own, and is purely an orthographic device. Its function is to separate a number of prefixes ending in a consonant from a following morpheme that begins with an iotated vowel. It is therefore commonly seen in front of the letters "я", "ё", "е", and "ю" (ja, jo, je, and ju in Russian). The hard sign marks the fact that the sound [j] continues to be heard in the composition. Example:
- съёмка ([ˈsjomkə]): "filming"
- Сёмка ([ˈsʲomkə]): diminutive form of the male name Семён (Simon)
It therefore functions as a kind of "separation sign" and has been used only sparingly in the aforementioned cases since the spelling reform of 1918. The consonant before the hard sign often becomes somewhat softened (palatalized) due to the following iotation. As a result, in the twentieth century there were occasional proposals to eliminate the hard sign altogether, and replace it with the soft sign ь, which always marks the softening of a consonant. However, in part because the degree of softening before ъ is not uniform, these proposals were never implemented. The hard sign ъ is written after both native and borrowed prefixes. In recent years, it has sometimes been seen in borrowed words before the letter и, to mark a greater separation of the constituent syllables. Such written usage has not yet been formally codified (See also Russian phonology and Russian orthography).
Prior to 1918, a hard sign was normally written at the end of a word when following a non-palatal consonant, even though it had no effect on pronunciation. For example, modern человек "man" was written человѣкъ, using a final hard sign as well as the old yat vowel ѣ, which had merged in pronunciation with the vowel е by the 18th century. These old usages were eliminated by the spelling reform of 1918, near the beginning of Bolshevik rule after the 1917 October Revolution. Because of the way this reform was implemented, the issue became politicized, leading to a number of printing houses in Petrograd refusing to follow the new rules. To force these printing houses to comply, red sailors of the Baltic Fleet confiscated type carrying the “letter parasites”. Printers were forced to use a non-standard apostrophe for the separating hard sign, for example:
- pre-reform: съѣздъ
- transitional: с’езд
- post-reform: съезд
In the beginning of the 1920s the hard sign was gradually restored as the separator. The apostrophe was still used afterward on some typewriters which did not include the hard sign, which became the rarest letter in Russian.
According to the rough estimation presented in Lev Uspensky's popular linguistics book A Word On Words (Слово о словах), which expresses strong support to the reform, the final hard sign occupied about 3.5% of the printed texts and essentially wasted a considerable amount of paper, which provided the economic grounds to the reform.
Printing houses set up by the emigrants from Russia kept using the pre-reform orthography for some time, however gradually they adopted the new spelling. Meanwhile, in the USSR the Dahl’s Explanatory Dictionary was repeatedly (1935, 1955) reprinted in compliance with the old rules of spelling and alphabet.
Today the final yer is sometimes used in Russian brand names – for example, Kommersant Коммерсантъ. Such usage is often inconsistent, as the copywriters may apply the simple rule of putting the hard sign after a consonant at the end of a word, but ignore the other outdated spelling rules. It is also sometimes encountered in humorous personal writing.
Bulgarian language 
In Bulgarian, the er golyam ( "ер голям" ) is used for the phoneme representing the mid back unrounded vowel (IPA /ɤ̞/), sometimes also notated as a schwa (/ə/). It sounds somewhat like the vowel sound in some pronunciations of "but" [bʌ̘t].
Belarusian language 
The letter is absent in the alphabets of Belarusian. In the Cyrillic Belarusian alphabet its functions are performed by the apostrophe or й. In the Latin Belarusian alphabet (Łacinka), functions of soft and hard signs are performed by j.
Ukrainian language 
Ossetian language 
In Ossetian, the hard sign has no phonetic value of its own, but is part of the digraphs гъ, къ, пъ, тъ, хъ, цъ, чъ.
Related letters and other similar characters 
Computing codes 
|Unicode name||CYRILLIC CAPITAL LETTER HARD SIGN||CYRILLIC SMALL LETTER HARD SIGN|
|UTF-8||208 170||D0 AA||209 138||D1 8A|
|Numeric character reference||Ъ||Ъ||ъ||ъ|
|KOI8-R and KOI8-U||255||FF||223||DF|
|Code page 855||159||9F||158||9E|
|Code page 866||154||9A||234||EA|
- "Лексикон" Валерия Скорбилина Архив выпусков программы, «ЛЕКСИКОН» № 238, интервью с Натальей Юдиной, деканом факультета русского языка и литературы
- Слово о словах, Лев Успенский, Лениздат, 1962, p. 156
- Артемий Лебедев, Ководство, § 23. Немного о дореволюционной орфографии.