In phonetics, a vowel is a sound in spoken language, such as an English "ah!" or "oh!" , with two competing definitions. In the more common phonetic definition, a vowel is a sound pronounced with an open vocal tract so that the tongue does not touch the lips, teeth, or roof of the mouth. There is no build-up of air pressure at any point above the glottis. This contrasts with consonants, such as English "sh!" , which have a constriction or closure at some point along the vocal tract. In the other, phonological definition, a vowel is defined as syllabic, the sound that forms the peak of a syllable. A phonetically equivalent but non-syllabic sound is a semivowel.