Avagraha

Avagraha (ऽ) is a symbol used to indicate prodelision of an अ  in many Indian languages like Sanskrit as shown below. It is usually transliterated with an apostrophe in Roman script and, in case of Devanagari, as in the Sanskrit philosophical expression शिवोऽहम् ' ('), which is a sandhi of (शिवः + अहम्) ‘I am Shiva’. The avagraha is also used for prolonging vowel sounds in some languages, for example Hindi माँऽऽऽ! for ‘Mā̃ā̃ā̃ā̃!’ when calling to one's mother, or when transliterating foreign words in instant messaging: for example, 'cool' can be transliterated as कूऽल.

In the case of Hindi, the character is also sometimes used as a symbol to denote long or heavy syllables, in metrical poetry. For example, the syllables in the word छंदः  ‘metre’ (in nominative) can be denoted as "ऽऽ", meaning two long syllables. (Cf. other notations in entry "Systems of scansion".)

Avagraha in Unicode
The avagraha symbol is encoded at several Unicode points, for various Brahmic scripts that use it.