<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> 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 . </P> <P> 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 . </P>

Why w and y are called semi vowels