Semi-vowel

In phonetics and phonology, a semivowel or glide, also known as a non-syllabic vocoid, is a sound that is phonetically similar to a vowel sound but functions as the syllable boundary, rather than as the nucleus of a syllable. Examples of semivowels in English are the consonants y and w, in yes and west. Written /j w/ in IPA, y and w are near to the vowels ee and oo in seen and moon, written /iː uː/ in IPA.

Semivowels form a subclass of approximants. Although "semivowel" and "approximant" are sometimes treated as synonymous, most authors agree that not all approximants are semivowels although the exact details may vary from author to author. For example, Ladefoged & Maddieson (1996) do not consider the labiodental approximant [ʋ] to be a semivowel while Martínez Celdrán (2004) proposes that it should be considered one.

In the International Phonetic Alphabet, the diacritic attached to non-syllabic vowel letters is U+032F ̯ COMBINING INVERTED BREVE BELOW. When there is no room for the tack under a letter, it may be written above, using U+0311 ̑ COMBINING INVERTED BREVE. Sometimes, the "extra-short" diacritic (U+0306 ̆ COMBINING BREVE) is used instead, which is not a completely correct transcription.

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