vowel

Short definition from Wiktionary

Noun

1. 1
   A sound produced by the vocal cords with relatively little restriction of the oral cavity, forming the prominent sound of a syllable.
2. 2
   A letter or diacritic representing the sound of a vowel; in English, the vowels are a, e, i, o, u, w (rarely), y (sometimes).

Verb

1. 1
   To add vowel points to a consonantal script (e.g. niqqud in Hebrew or harakat in Arabic).