What is an individual letter or character used in a poetic meter (Chhanda) called?

In Hindi prosody (Chhanda Shastra), an individual character or letter is referred to as a 'वर्ण' (Varna). It includes both short and long vowels or consonants attached to vowels. 'मात्रा' (Matra) refers to the time taken to pronounce a varna, and 'चरण' (Charan) represents the quarters or lines of the stanza.