International Alphabet of Sanskrit Transliteration
The International Alphabet of Sanskrit Transliteration (I.A.S.T.) is a transliteration scheme that allows a lossless romanization of Indic scripts as employed by the Sanskrit language. It is also used to romanize Pāḷi, Prākṛta and Apabhraṁśa. It is based on the notation used by Monier Monier-Williams in his 1899 dictionary.
Use
IAST is commonly used for books dealing with ancient Sanskrit and Pāḷi topics related to Indian religions. The script is, however, insufficient to represent both Sanskrit and Pāḷi on the same page properly because the ḷ (l with underdot), a vowel in Sanskrit (vocalic /l/), is the retroflex consonant in Pāḷi ([ɭ]). It is better to follow Unicode and ISO 15919, which is, in any case, a more comprehensive scheme.
IAST is based on a standard established by the International Congress of Orientalists at Geneva in 1894. It allows a lossless transliteration of Devanāgarī (and other Indic scripts, such as Śāradā script); and, as such, it represents the phonemes of Sanskrit and also allows essentially phonetic transcription: visarga ḥ is an allophone of word-final r and s.