Coalescence

Coalescence is a special kind of assimilation. With all the other types of assimilation discussed before, it’s usually either the consonant on the left or the right that has a dominating influence on the other. In coalescence, both consonants influence each other and fuse together to form a new one, often an affricate.

Yod-Coalescence

This type of coalescence involves a fusion of an alveolar plosive or fricative, followed by a semi-vowel /j/ and a back vowel, either /uː/, /ʊ/ or /oː/. This is generally manifested in forms of the pronoun you, such as in would you, could you, should you, did you or he/she knows your name.

Transcribe the sample expressions shown above using the transcription editor. Keep the editor window/tab open afterwards, as you’ll need it again.
Try to think of some further examples.
Can you think of any particular speech style or situation where this may not be applicable/appropriate?

‘U-Coalescence’

What I have here termed ‘u-coalescence’ also involves a combination of alveolar plosive/fricative and usually a <u> in spelling, but without a graphemic indication of an intervening semi-vowel, i.e. a <y>. It commonly occurs in words like tune, dune, fortune, pro-/de-/re-/induce, century, nature/natural, (un)usual, mixture, texture, picture, pressure, creature, opportunity, situation, actually, pleasure or treasure in the speech of many speakers of (British) English.

Some other words or constructions, such as assume, stupid, student, substitute, opportunity, promised yesterday or as yet often exhibit this kind of coalescence, too, but seem to be somewhat more optional, especially the words beginning with <st>.

Again, transcribe the above sample expressions, but this time also pay particular attention to potential reductions/weak forms.
To what extent does your accent allow you not to coalesce in these expressions?
Think about whether you’ve heard someone else not use coalescence in these or similar examples and what kind of impression you may get if you hear this.

Sources & Further Reading:

Cruttenden, A. (1994). Gimson’s Pronunciation of English (5th ed.). London: Edward Arnold.