ISO 15919 is an international standard on the romanization of many Indic scripts, which was agreed in 2001 by a network of the national standards institutes of 157 countries. United Nations Romanization Systems for Geographical Names (UNRSGN) is a standard developed by the United Nations Group of Experts on Geographical Names (UNGEGN) and covers many Indic scripts.
ALA-LC was approved by the Library of Congress and the American Library Association and is a US standard. IAST is not a standard as no formally approved document exists for it but a convention developed in Europe for the transliteration of Sanskrit rather than that of Indic scripts.
As a notable difference, both international standards, ISO 15919 and UNRSGN transliterate anusvāra as ṁ, while ALA-LC and IAST use ṃ for it.
The table below shows the differences between ISO 15919, UNRSGN and IAST for Devanagari transliteration.
| Devanagari | ISO 15919 | UNRSGN | IAST | Comment |
|---|---|---|---|---|
| ए / े | e | To distinguish between long and short 'e' in Dravidian languages. 'E' now represents ऎ / ॆ. | ||
| ओ / ो | o | To distinguish between long and short 'o' in Dravidian languages. 'O' now represents ऒ / ॊ. | ||
| ऌ / ॢ | l̤ | In ISO 15919, ḷ is used to represent ळ. | ||
| ॡ / ॣ | For consistency with l̥ | |||
| ं | ṁ | In ISO 15919, ṃ is used to specifically represent Gurmukhi Tippi ੰ. | ||
| ऋ / ृ | ṛ | In ISO 15919, ṛ is used to represent ड़. | ||
| ॠ / ॄ | ṝ | For consistency with r̥ | ||