In phonetics, a vowel is a sound in spoken language that is characterized by an open configuration of the vocal tract so that there is no build-up of air pressure above the glottis. This contrasts with consonants, which are characterized by a constriction or closure at one or more points along the vocal tract. A vowel is also understood to be syllabic: an equivalent open but non-syllabic sound is called a semivowel. Category: