The Vowel अ: Where Devanagari Begins
Launch library · evergreen read

अ is the first vowel of the Devanagari alphabet and the default sound carried inside every consonant unless marked otherwise. Every script has to start somewhere, and Devanagari begins with this short, open vowel, close to the a in the English word about. What makes अ unusual for English speaking learners is that it is often invisible.
A bare consonant like क already contains this vowel sound built in, so क alone is pronounced ka, not k. Devanagari assumes अ unless another vowel sign replaces it. Understanding अ early makes the rest of the script far easier to follow. Once a learner accepts that consonants come with a built in vowel.
The logic behind matras, the vowel signs discussed elsewhere, starts to make much more sense. A simple way to test this understanding is writing a few bare consonants, क, प, त, and reading each one aloud with its built in अ sound automatically included, without needing any additional vowel mark attached.