IAST

 IAST stands for International Alphabet of Sanskrit Transliteration.

It is a standardized system used to write Sanskrit (and related Indic languages) in the Roman alphabet with precise diacritical marks.

Why IAST is used

• It preserves exact Sanskrit pronunciation.
• It distinguishes sounds that English cannot normally show.
• It is widely used in academic, philosophical, and scriptural texts.

Example (from 

Bhagavad Gita

 10.41)

Devanagari:

यद् यद् विभूतिमत् सत्त्वं श्रीमदूर्जितमेव वा

IAST:

yad yad vibhūtimat sattvaṁ śrīmad ūrjitam eva vā

What the marks mean

• ā ī ū = long vowels
• ṛ ḷ = special Sanskrit vowel sounds
• ś ṣ = different “sh” sounds
• ṭ ḍ ṇ = retroflex (tongue curled back) sounds
• ṁ ḥ = nasal / breath sounds

In simple terms:

IAST is a scientific spelling system that helps pronounce Sanskrit correctly without using the Devanagari script.

If you’d like, I can also show how it differs from simple English transliteration.