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Visarga (IAST: visarga) (Sanskrit: विसर्गः Tamil-aytam) meaning "sending forth, discharge". In Sanskrit phonology (śikṣā), visarga (also called, equivalently, visarjanīya by earlier grammarians) is the name of a phone, [h], written as:
Visarga is an allophone of /r/ and /s/ in pausa (at the end of an utterance). Since /-s/ is a common inflectional suffix (of nominative singular, second person singular, etc.), visarga appears frequently in Sanskrit texts. In the traditional order of Sanskrit sounds, visarga together with anusvāra appears between vowels and stop consonants.
The precise pronunciation of visarga in Vedic texts may vary between Śākhās. Some pronounce a slight echo of the preceding vowel after the fricative, for example aḥ will be pronounced [ɐhᵄ], and iḥ will be pronounced [ihⁱ].
Types of Visarga
According to Sanskrit phonologists, the visarga has two allophones, namely जिह्वामूलीय (Jihvāmūlīya or the guttural visarga) and उपध्मानीय (Upadhmānīya or the fricative visarge). It is in fact the latter which we commonly find in writing resembling the punctuation mark of colon or as two tiny circles one above the other. This form is retained by most Indian scripts to date. The former is pronounced before the letters क, ख, प and फ. e.g. तव पितामहः कः | (Who is your grand father?) पक्षिणः खे उत्पतन्ति |(Birds fly in the sky) भोः पाहि (Sir, saveme) तपःफलम् (Result of penances) etc. The Jihvāmūlīya visarga is written as two crescent-shaped semi-circles one above the other, facing the top and bottom respectively. This mode of showing the grammatical rule pertaining to the Jihvāmūlīya is still extant in the Telugu script and the Kannada alphabet while the allophone was completely lost in all other Indian scripts. .....nowadays it is used for only Sandi
In Tamil, the visarga is called āytam, written ஃ. Apart from a modern use as a diacritic to write foreign sounds, it is archaic and employed only in idiomatic and fossilized words such as அஃது (adhu - "there"), இஃது (idhu - "here") etc. It is mentioned in the earliest available Tamil grammatical treatise, Tolkāppiyam (1:1:2), where it is categorized as an allophone (cārpezuttu "dependent sound"). As stated by Krishnamurti (Krishnamurti:2003 p154  ) "The properties of āytam, as described by Tolkāppiyam, were: (1) it occurred after a short vowel and before a stop (voiceless), and its place of articulation is like that of the stop. In other words, ஃ assimilates to the following voiceless stop".
In the Burmese script, the visarga (variously called ရှေ့ကပေါက် shay ga pauk, ဝစ္စပေါက် wizza pauk, or ရှေ့ဆီး shay zi and represented with two dots to the right of the letter as ◌း), when used with joined to a letter, creates the high tone.
Motoori Norinaga invented a mark for visarga which he used in a book about Indian orthography.