Page "Manner of articulation" Paragraph 20

:* One use of the word semivowel, sometimes called a glide, is a type of approximant, pronounced like a vowel but with the tongue closer to the roof of the mouth, so that there is slight turbulence.

In English, / w / is the semivowel equivalent of the vowel / u /, and / j / ( spelled " y ") is the semivowel equivalent of the vowel / i / in this usage.

Other descriptions use semivowel for vowel-like sounds that are not syllabic, but do not have the increased stricture of approximants.

These are found as elements in diphthongs.

The word may also be used to cover both concepts.