vowelglide

Vowel glide, also called a glide or semivowel, is a class of speech sounds that are vowel-like in articulation but function as consonants within the syllable structure. Glides are typically sonorants that occur in syllable onsets and do not form the nucleus of a syllable. They are produced with a relatively open vocal tract and a high or mid tongue position, but with enough constriction to behave like consonants.

The two core glides found in many languages are the palatal approximant [j] (as in yes) and the labio-velar approximant [w] (as in wet). Some languages have additional glides or variation in their vowel-like consonants, and in some phonological analyses these sounds are treated as a separate consonant category rather than as part of the vowel inventory.

Glides are distinguished from vowels by their distribution and phonological function: they typically occur at the beginning of syllables or in onset clusters and do not serve as the syllable nucleus. They differ from many consonants in their smooth, relatively turbulence-free articulation and their tendency to be voiced.

Articulatorily, glides are described as high or mid tongue positions with a relatively open pharyngeal configuration, producing a resonance closer to vowels than to most obstruents. Phonologically, they often function as transitions into the following vowel, creating a smooth glide from the consonant-like articulation into the vowel nucleus. In many languages, glides participate in diphthongal sequences or appear in rapid speech as vowel-like variants. Historically, glides can arise from vowels or shift toward vowel qualities in certain phonological processes, leading to variation across languages.