Semivowel

Certain sounds, 'j' and 'w', are intermediate and must be considered to display features that are commonly attributed to vowels and consonants. On the one hand, they are produced with no perceived structure in the air stream which makes them much like vowels, yet based on their typical position in the sequence of consonants and vowels in the syllable, they must be said to function as consonants. Such sounds are therefore often referred to as semivowels.

Examples in the English sound system are the labiodental and palatal frictionless continuants. These sounds are partially consonantal and partially vocalic, hence, one often encounters the functional term semivowel rather than the phonetic term continuant. These sounds are vocalic as they are voiced and no stricture is involved in their production, but they can become voiceless if preceded by a voiceless stop, as for example in 'queue' and 'pew'. Both sounds are also produced in a manner similar to high vowels. The two semivowels [j] in 'you' and [w] in 'won' are however consonantal in that they cannot function alone in syllables.