Editing Soft sign (section)

=== Before a vowel in East Slavic languages ===
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 {{IPA|/lʲjut/}} '(they) pour/cast' and лют {{IPA|/lʲut/}} '(he is) fierce'). The feature, quite consistent with [[Russian orthography]], promulgated a confusion between palatalization and iotation, especially because {{angbr|ь}} usually precedes so-called ''soft vowels''. Combinations {{angbr|ья}} (ya), {{angbr|ье}} (ye), {{angbr|ьё}} (yo) and {{angbr|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. <!-- write something about Ukrainian ї and є, I know that ї is always iotated, but am not sure about є. --> In those cases, {{angbr|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 {{angbr|ьи}} (yi) nor for {{angbr|ьо}} (yo), because these vowels are not iotated in isolation. The latter case, though, is rarely used in Russian (only in loanwords such as {{angbr|бульон}}) and can be seen as a replacement of phonetically identical {{angbr|ьё}}, which gets rid of an "inconvenient" letter {{angbr|[[ё]]}}. In Ukrainian and Bulgarian, the spelling {{angbr|ьо}} indicates palatalization, not iotation.

Known as the ''[[hard sign]]'' ({{langx|ru|твёрдый знак|tvjordyj znak}}, {{IPA|ru|ˈtvʲɵrdɨj ˈznak|pron}}), {{angbr|ъ}}, an "unpalatalization sign", also denotes iotation, as in the case of {{angbr|ъя}}, {{angbr|ъе}}, {{angbr|ъё}} and {{angbr|ъю}} in Russian. It differs from the soft sign in that it does not necessarily soften the preceding consonant like the soft sign does (although consonants preceding the hard sign are still sometimes softened).

Similarly, the soft sign may denote iotation in [[Belarusian language|Belarusian]] and [[Ukrainian language|Ukrainian]], but it is not used so extensively as in Russian. [[Ukrainian orthography|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 preceded by an iotated vowel is palatalized.