The International Alphabet of Sanskrit Transliteration (IAST) is a popular transliteration scheme that allows a lossless romanization of Indic scripts.
IAST is the most popular transliteration scheme for romanization of Sanskrit and Pāḷi. It is often used in printed publications, especially for books dealing with ancient Sanskrit and Pāḷi topics related to Indian religions. With the wider availability of Unicode fonts, it is also increasingly used for electronic texts.
The script is, however, insufficient to represent both Sanskrit and Pāḷi on the same page properly, owing to confusion of the vowel l sign in Sanskrit (here ḷ) and the need for the same sign for the retroflexive consonant ḷ, which is found in Pāḷi. Here 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 represents not only the phonemes of Sanskrit, but allows essentially phonetic transcription (e.g. Visarga ḥ is an allophone of word-final r and s).
The National Library at Kolkata romanization, intended for the romanization of all Indic scripts, is an extension of IAST.
IAST sign inventory and conventions
The sign inventory of IAST (both small and capital letters) shown with Devanāgarī equivalents and phonetic values in IPA, is as follows (valid for Sanskrit; for Hindi, some minor phonological changes have occurred):
|aspirated unvoiced stops|
|aspirated voiced stops|
| ||य [j]|
| ||श [ɕ]|
| || || || ||voiced fricative|
Note: Unlike ASCII-only romanizations such as ITRANS or Harvard-Kyoto, the diacritics used for IAST allow capitalization of proper names. The capital variants of letters never occurring word-initially (Ṇ Ṅ Đ Ṝ) are only useful in Pāṇini contexts, where the convention is to typeset the IT sounds as capital letters (see Aṣṭādhyāyī).
Comparison with ISO 15919
For the most part, IAST is a subset of ISO 15919. The following five exceptions are due to the ISO standard accommodating an extended repertoire symbols to allow transliteration of Devanāgarī and other Indic scripts as used for languages other than Sanskrit.
|ए/ े||e||ē||ISO e represents ऎ/ ॆ.|
|ओ/ो||o||ō||ISO o represents ऒ/ॊ.|
| ं||ṃ||ṁ||ISO ṃ represents Gurmukhi Tippi ੰ.|
|ऋ/ ृ||ṛ||r̥||ISO ṛ represents ड़ /ɽ/.|
|ॠ/ ॄ||ṝ||r̥̄||for consistency with r̥.|