Ad. [w] and [j] became [u] and [i] before consonants and finally; [wC|-w|jC|-j] > [uC|-u|iC|-i]

Ad. [w] and [j] became [u] and [i] before consonants and finally; [wC|-w|jC|-j] > [uC|-u|iC|-i]

Tolkien stated that the semi-vowel [w] was vocalized to the vowel [u] when appearing before a consonant or finally. In similar conditions the semi-vowel [j] became [i] (SD/419).

There is some ambiguity of whether this w/y-vocalization happened before or after [ɣ] assimilated to preceding voiced consonants. Either way, the net result would have been the same. In the first case, ✶[wɣV/yɣV] would have become [uɣV/iɣV] and thereafter [uwV/uyV] when [ɣ] became [w], [j] between [u], [i] and another vowel. In the second case, the [ɣ] in ✶[wɣV/yɣV] would have assimilated to [wwV/yyV] before the vocalization could apply, and thereafter became [uwV/uyV]. The discussion here assumes w/y-vocalization happened first, since it simplifies some other rules. See the word ✶dāw’r for more evidence that this vocalization was early.

Reference ✧ SD/419

Related

Phonetic Rule Elements

[wC|-w] > [uC|-u] ✧ SD/419 ([wC|-w] > [uC|-u])
[jC|-j] > [iC|-i] ✧ SD/419 ([yC|-y] > [iC|-i])

Phonetic Rule Examples

izrajji > izraiji jC|-j > iC|-i ✶Ad. izray+yi > izrai+yi > izrēyi > izrêi > Ad. izrê ✧ SD/424
dāwr > dāur wC|-w > uC|-u ✶Ad. dāw’r > Ad. dâur ✧ SD/423
khāw > khāu wC|-w > uC|-u ✶Ad. khāw > Ad. khâu ✧ SD/426
khaw > khau wC|-w > uC|-u ✶Ad. khăw > Ad. khō ✧ SD/426
manaw > manau wC|-w > uC|-u ✶Ad. manaw- > manau > Ad. manō ✧ SD/424
manawji > manauji wC|-w > uC|-u ✶Ad. manaw+yi > manau+yi > manōyi > Ad. manôi ✧ SD/424