A and the Rules That Join Words

The short a is the sound the Sanskrit rules of junction are built around, because it is the vowel most often standing at the seam where two words meet. When a word ending in a meets a word beginning in a, the two combine into a single long vowel and the seam disappears. When a meets i the result is neither a nor i but e, and when a meets u the result is o, which is why the grammarians class e and o as compound vowels rather than simple ones and place them after the a, i and u series in the order rather than among them. Those three rules alone rewrite the surface of a Sanskrit sentence, and the writing follows the pronunciation rather than the underlying words, so a reader has to undo the junction to find where one word ends and the next begins.

The letter also carries the language's commonest prefix. Placed at the head of a stem, a negates it: the word for non-injury is the same word as injury with this vowel in front, and the terms for the endless, the unborn and the unmanifest are formed the same way. Before a vowel the prefix takes a nasal and becomes an, which is the same alternation English inherited independently in a and an. Because that prefix begins a word, it is one of the few places where the independent letter has to be written at all rather than sitting unmarked inside a consonant sign, so a Brahmi inscription shows this vowel in its full form far more often at the start of a negated word than anywhere else.