In phonetics and phonology, a semivowel, glide or semiconsonant 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 y and w in yes and west, respectively. Written in IPA, y and w are near to the vowels ee and oo in seen and moon, written in IPA. The term glide may alternatively refer to any type of transitional sound, rather than necessarily a semivowel.