Page "Consonant" Paragraph 8

One blurry area is in segments variously called semivowels, semiconsonants, or glides.

On the one side, there are vowel-like segments that are not in themselves syllabic but that form diphthongs as part of the syllable nucleus, as the i in English boil.

On the other, there are approximants that behave like consonants in forming onsets but are articulated very much like vowels, as the y in English yes.

Some phonologists model these as both being the underlying vowel, so that the English word bit would phonemically be, beet would be, and yield would be phonemically.

Likewise, foot would be, food would be, wood would be, and wooed would be.

However, there is a ( perhaps allophonic ) difference in articulation between these segments, with the in yes and yield and the of wooed having more constriction and a more definite place of articulation than the in boil or bit or the of.