A Vowel Made of a Consonant

A syllabic r carries a syllable with no other vowel beside it, which is a familiar enough thing in the world's languages but unusual among the neighbours of Old Indo-Aryan, and the Indian phoneticians handled it by classing the sound with the vowels outright rather than treating it as a consonant behaving oddly. That decision is what puts the letter in the vowel section of the order, seventh in the sequence, with its own short and long pair like any other vowel. It also means the sound takes vowel endings, participates in the ladder of strengthening, and is written with a vowel mark rather than with a consonant sign.

The strengthening is where the sound is most often met. Raised one grade the syllabic r becomes the sequence ar, and raised a second it becomes aar, so a root containing this vowel appears with a plainly different shape whenever a suffix calls for a stronger grade. That single alternation accounts for a large number of Sanskrit word families whose members look unrelated until the ladder is applied to them. The letter is also the first sound of a set of words that travelled well beyond Sanskrit, including the name of the oldest of the Vedic collections and the name of the deity most widely worshipped across the subcontinent under a form of it.