Vowel

[Sarah]

A vocal, or sometimes a whispered, sound modified by resonancein the oral passage, the peculiar resonance in each case giving toeach several vowel its distinctive character or quality as a sound ofspeech; -- distinguished from a consonant in that the latter, whethermade with or without vocality, derives its character in every casefrom some kind of obstructive action by the mouth organs. Also, aletter or character which represents such a sound. See Guide toPronunciation, §§ 5, 146-149.

[Luis Fok]

A speech sound which is produced by comparatively open configuration of the vocal tract, with vibration of the vocal cords but without audible friction, and which is a unit of the sound system of a language that forms the nucleus of a syllable.