in grammar, a letter which affords a complete sound of itself, or a letter so simple as only to need a bare opening of the mouth to make it heard, and to form a distinct voice.

The vowels are six in number, viz. A, E, I, O, U, Y, and are called vowels, in contradistinction to certain other letters, which, depending on a particular application of some part of the mouth, as the teeth, lips or palate, can make no perfect sound without an opening of the mouth, that is, without the addition of a vowel, and are therefore called consonants.