1. A speech sound that is produced by comparatively open configuration of the vocal tract, with vibration of the vocal cords but without audible friction.
The letter 'a' is a vowel in English.
A letra 'a' é uma vogal em português.
2. Any of the letters representing vowel sounds in the alphabet (a, e, i, o, u in Portuguese).
Portuguese has five main vowels.
O português tem cinco vogais principais.