Two Laterals, and Then Three

The received Brahmi order holds two laterals apart, the dental one and the retroflex one that stands last among the consonants. Indo-Aryan needs no more. The Dravidian languages of the far south need a third, and Tamil-Brahmi supplied it, adding a letter for a retroflex approximant made with the tongue drawn back without touching the roof of the mouth. That sound is among the most characteristic of Tamil and it has no Indo-Aryan counterpart at all.

Where the additional letter was placed says something about how these alphabets grow. It went at the end of the order, after the retroflex lateral that already closed the consonants, rather than beside the laterals it belongs with phonetically. That is the standing convention: the order is a memorised sequence and additions are filed at the end of it, because inserting a letter in the middle would oblige every reciter to relearn the list.

The same convention governs the retroflex lateral itself, which sits after the aspirate rather than among the laterals, and the dotted letters that the northern scripts later added for Persian and Arabic sounds, which are filed under the letters they modify. An alphabet that is recited grows at its edges, and where a letter sits in the order is often a fact about its history rather than about its sound.