S. [iu] and [ju] became [ȳ]; [{ij}u|jui] > [ȳ|jui]

S. [iu] and [ju] became [ȳ]; [{ij}u|jui] > [ȳ|jui]

In Sindarin, the diphthong [iu] developed into [ȳ], a change mentioned in The Lord of the Rings Appendix E (LotR/1115), and also in a chart describing the phonetic development of diphthongs appearing in notes associated with Tolkien’s discussion of Hands, Fingers and Numerals from the late 1960s (VT48/7). In both cases, it seems this phonetic development was the result of both original primitive [iu] as well as the diphthongs that developed when primitive [eu] became [iu]. This sound change also occurred from initial yu- [ju-], as noted by David Salo (GS/§4.92, §4.93). He suggested [ju] > [jy] > [ȳ], but I think [ju] > [iu] > [ȳ] is also possible:

The change of [ju] > [ȳ] might have been inhibited where the u was already part of a diphthong, as in N. iuith [juiθ] “use”, as was also suggested by David Salo (GS/§4.93). Since the Noldorin phonetic developments of these diphthongs were different than Sindarin, it’s hard to say for sure.

Conceptual Development: Other than a general merging of primitive [eu] and [iu], these phonetic developments were quite different at earlier conceptual stages of the language. See the entry on how [eu] became [iu] for further details, along with more examples of this sound change.

Reference ✧ LotR/1115 ✧ for example: y < ✶eu, y < ✶iu

Order (01200)

Before 05000 [au], [ae] became [o], [e] in polysyllables keu̯rānă > cýrawn > S. cýron VT48/7

Phonetic Rule Elements

[iu] > [ȳ] ✧ LotR/1115 (eu > y); LotR/1115 (iu > y); VT48/7 (iu > ȳ)
[ju] > [ȳ]
[jui] > [jui]

Phonetic Rule Examples

diule > dȳle iu > ȳ deulē > S. dýl ✧ PE17/151
diura > dȳra iu > ȳ DEWE > S. dýr ✧ PE17/151
kiule > kȳle iu > ȳ keule > S. cŷl ✧ VT48/8
kiura- > kȳra- iu > ȳ kewe > S. cýra ✧ VT48/7
kiura > kȳra iu > ȳ keu-rā > S. cŷr ✧ VT48/8
kiurǭna > kȳrǭna iu > ȳ keu̯rānă > cýrawn > S. cýron ✧ VT48/7
liuka > lȳka iu > ȳ LEWEK > S. lýg ✧ PE17/160
iu > ȳ iu > ȳ eu > S. y ✧ LotR/1115
julma > ȳlma ju > ȳ julmā > S. ylf ✧ WJ/416
jūneke > ȳneke ju > ȳ yūneke > S. ýneg ✧ VT47/41