One of the two most basic verbs in Sanskrit begins with this letter, the root meaning to be or to become, and it supplies both the ordinary present tense of the verb to be and an enormous derived vocabulary. The words for existence, for a state of being, for the world, for a living creature and for what has come to pass are all built on it, and so is the term for worldly existence in the religious literature of the subcontinent.
A second root beginning with the same letter means to share, to apportion or to be devoted, and it produces the word for devotional participation that names one of the great movements in Indian religion, along with the title for a lord or a blessed one that is applied to deities and to teachers across several traditions. Between these two roots the letter is at the head of a very large share of the religious vocabulary of South Asia.
It is correspondingly frequent in inscriptions of every period, which is convenient for a palaeographer. Where a letter is common the shapes can be compared across many dated examples, and the sequence of forms is firm rather than reconstructed. Letters like the aspirated palatal, which the language barely uses, offer nothing like the same evidence and are dated by inference from their neighbours instead.