|This article does not cite any references or sources. (December 2008)|
Visarga (visarga) (Sanskrit: विसर्गः) is a Sanskrit word 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 IAST ⟨ḥ⟩, Harvard-Kyoto ⟨H⟩, Devanagari ⟨ः⟩. The circle stands in for a consonant and is not an actual letter; the two dots on the right form the Visarga.
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 shakhas. 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].
Other Languages 
Tamil (āytam) 
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".
Burmese (shay ga pauk) 
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.