I with grave (Cyrillic)

Slavic letters
А Б В Г Ґ Д Ђ Ѓ Е Ѐ Ё Є Ж З Ѕ И Ѝ І Ї Й Ј К Л Љ М Н Њ О П Р С Т Ћ Ќ У Ў Ф Х Ц Ч Џ Ш Щ Ъ Ы Ь Э Ю Я
Non-Slavic letters
Ӑ А̄ А̊ А̃ Ӓ Ӓ̄ Ә Ә́ Ә̃ Ӛ Ӕ Ғ Г̧ Г̑ Г̄ Ҕ Ӻ Ӷ Ԁ Ԃ Ꚃ Ꚁ Ꚉ Ԫ Ԭ С́ Ӗ Е̄ Е̃ Ё̄ Є̈ Ӂ Җ Ꚅ Ӝ Ԅ Ҙ Ӟ З́ Ԑ Ԑ̈ Ӡ Ԇ Ӣ И̃ Ҋ Ӥ Қ Ӄ Ҡ Ҟ Ҝ Ԟ Ԛ Ӆ Ԯ Ԓ Ԡ Ԉ Ԕ Ӎ Ӊ Ң Ԩ Ӈ Ҥ Ԣ Ԋ О̆ О̃ О̄ Ӧ Ө Ө̄ Ӫ Ҩ Ԥ Ҧ Р̌ Ҏ Ԗ Ҫ Ԍ Ꚑ Ҭ Ꚋ Ꚍ Ԏ У̃ Ӯ Ӱ Ӱ́ Ӳ Ү Ү́ Ұ Х̑ Ҳ Ӽ Ӿ Һ Һ̈ Ԧ Ꚕ Ҵ Ꚏ Ҷ Ӵ Ӌ Ҹ Ꚓ Ꚗ Ꚇ Ҽ Ҿ Ы̆ Ы̄ Ӹ Ҍ Э̆ Э̄ Э̇ Ӭ Ӭ́ Ӭ̄ Ю̆ Ю̈ Ю̈́ Ю̄ Я̆ Я̄ Я̈ Ԙ Ԝ Ӏ
Archaic letters
Ꙁ Ꙃ Ꙅ Ꙇ Ꙉ Ҁ Ѻ ОУ Ꙋ Ѡ Ѽ Ꙍ Ѿ Ꙏ Ѣ Ꙑ Ꙓ Ꙕ Ꙗ Ѥ Ѧ Ꙙ Ѫ Ꙛ Ѩ Ꙝ Ѭ Ѯ Ѱ Ѳ Ѵ Ѷ Ꙟ Ꙡ Ꙣ Ꙥ Ꙧ Ꙩ Ꙫ Ꙭ ꙮ Ꚙ Ꚛ
List of Cyrillic letters Cyrillic digraphs

I with grave (Ѝ ѝ; italics: Ѝ ѝ) is a character representing a stressed variant of the regular letter ⟨И⟩ in some Cyrillic alphabets, but none (either modern or archaic) includes it as a separate letter.

Most regularly ⟨Ѝ⟩ is used in Bulgarian and Macedonian languages to distinguish the short form of the direct object ⟨ѝ⟩ ('her') from the conjunction ⟨и⟩ ('and', 'also'), or less frequently, to prevent ambiguity in other similar cases. When not available, the character ⟨ѝ⟩ is often replaced by an ordinary ⟨и⟩ (not recommended, but still orthographically correct) or in Bulgarian by the letter ⟨й⟩ (formally this is considered a spelling error).

In modern (since the 17th century) Russian recension of Church Slavonic, ⟨Ѝ⟩ (or any other vowel with a grave accent) is just an orthographic variant of the same letter with an acute accent when used as the last letter of the word.

⟨Ѝ⟩ (as well as other vowels with acute, grave, circumflex, or double grave accents) can be optionally used in Serbian texts to show one of four possible tones of the stressed syllable. In cases like прѝкупити ('to gather') vs. прику́пити ('to purchase more'), or ѝскуп ('redemption' 'ransom') vs. и̏скуп ('meeting'); the usage of diacritics can also prevent ambiguity. In the Latin variant of the Serbo-Croatian writing system (the so-called Gajevica), all stress/tone marks are the same, i.e. Cyrillic ⟨Ѝ⟩ corresponds to Latin ⟨ì⟩ etc.

⟨Ѝ⟩ (as well as any other vowel with grave accent) can be found in older (up to the first decades of the 20th century) Russian and Ukrainian books as stressed variants of regular (unaccented) vowels, like Russian вѝна ('wines') vs. вина̀ ('guilt'). Recently, East Slavonic typographies have begun using the acute accent instead of the grave accent to denote the stress: ви́на, вина́.

Stress marks are optional in East Slavic languages. They are regularly used only in special books like dictionaries, primers, or textbooks for foreigners as the stress is very unpredictable in all three languages, whereas in general texts, they are extremely rare and used mainly to help prevent ambiguity in certain cases or to show pronunciation of exotic words.

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Wikipedia