Semivowels

Semivowels, also known as glides or approximants, are a class of speech sounds produced with a relatively open vocal tract and little or no friction. They function phonologically like consonants, typically occurring as part of syllable onsets rather than forming the nucleus of a syllable as vowels do. Semivowels are closely related to vowels in their articulation, hence the name, but they behave as consonants within syllable structure.

The two best-attested semivowels in many languages are the palatal approximant [j] (the sound of y in yes) and the labio-velar approximant [w] (the sound of w in we). They are generally voiced and sonorant, produced with a narrow constriction that is not enough to create turbulent noise. The tongue moves toward a vowel position during articulation, giving these sounds a glide-like, vowel-like feel. Lip rounding accompanies [w], while [j] involves a high, front tongue position.

Distribution and function vary cross-linguistically. In many languages, semivowels occur in onset clusters before vowels, as in words containing a y- or w- sound plus a following vowel. They may contrast with surrounding vowels or with other approximants, and in some languages they participate in diphthongs or vowel sequences as transitional sounds. Some analyses treat other approximants as semivowels, but the core set commonly recognized in mainstream phonetics comprises [j] and [w], with additional, language-specific variants.

In summary, semivowels are vowel-adjacent, consonantal sounds that are produced with a high degree of openness and are used in syllable onsets or as articulatory transitions, linking vowel and consonant categories in diverse languages.