Q. [ei], [ou] generally became [ī], [ū]; [ei|ou] > [ī|ū]

Q. [ei], [ou] generally became [ī], [ū]; [ei|ou] > [ī|ū]

The diphthongs ei, ou usually simplified to long ī, ū in Quenya. This change was not universal, however, and these diphthongs occasionally developed into other sounds, but the conditions under which the variant developments occurred as well as the resulting sounds gradually evolved throughout Tolkien’s life.

In the Early Qenya of the 1910s and 20s the common phonetic development was ei, ou > ai, au, such as:

One exception is ᴱ✶nēgittĕ > ᴱQ. neite “wax” (GL/60); this the only appearance of ei in an Early Qenya word, and the diphthong may have been preserved because it was derived from a long ēi.

In the Compative Tables of phonetic developments from the 1930s, Tolkien introduced ī, ū as alternate developments for ei, ou, so that ei > ī or ai and ou > ū or au (PE19/25), but Tolkien did not describe the conditions under which the various sound changes occurred. Looking at contemporaneous examples in The Etymologies, we see the following phonetic developments for (undeleted) entries:

Deleted entries show both ei > ī (Ety/GEY) and ei > ai (Ety/EY). For weı̯rē > Vaire Tolkien said this sound change was “owing to wei > wai”. Likewise, in the somewhat earlier Declension of Nounds [Version 4] from the early 1930s, Tolkien said that “ei > ai after ı̯”, giving the instrumental plural form of nie as niainen [nie + inen] to illustrate this phonetic development (PE21/6). These two examples seem to show yei, wei > yai, wai, but that does not explain ᴹ√NOWO > nause.

In the Outline of Phonetic Development [OP1] from the 1930s Tolkien introduced a new paradigm:

ei remained in AQ, but became in PQt. ē when it bore the PQ stress. But in unstressed syllables (according to PQt. accent), and in final syllables other than monosyllabic words it became [ī̆] ... Similarly ou remained in AQ; but became in PQt. where still stressed ō. Otherwise it became ū̆ (OP1: PE19/53).

According to these rules, ei, ou > ī, ū when unstressed and > ē, ō when stressed, and these sound changes occurred in Parmaquesta [PQ]. Tolkien described similar rules in the Outline of Phonology [OP2] from the 1950s:

ei remained in AQ, but became ē in PQ. This development occurred only in stressed syllables (according to the accentual system observable in Parmaquesta). In final syllables other than stressed monosyllables, and in unstressed medial syllables it became ī ... ou similarly remained in AQ, but became ō in PQ. Similarly ou > ū in unstressed (PQ) syllables (OP1: PE19/106).

However, the examples from the 1950s and later show ei, ou > ī, ū pretty consistently, even in positions where the diphthong would be stressed:

In a table of diphthongal developments from the late 1960s, Tolkien said:

CE: ei > Q. í (ē) ... [CE] ou > [Q.] ū (ō) ... ē after ı̯, y; ō after u̯, w (VT48/7).

Thus it seems that, like the 1930s, the special developments for ei, ou are once again conditioned for those diphthongs appearing after the semi-vowels y, w. These specialized developments are also mentioned in OP1 (PE19/53), as discussed in the entry on how [jei], [wou] became [jē], [wō]. This alternate pattern can be seen in a late discussion of the phonetic developments for the suffix -itë:

íte (from iti, eiti), éte (from eiti after i, y) (PE22/155).

As an example of this alterate development Tolkien gave √SKEY [> *skeyeite] > Q. xiéte “passing, impermanent”, though this development could also be the result of eye > ie. To summarize the typical developments in each conceptual period:

Note that is conceivable that the rules whereby “ei, ou > ē, ō when stressed” and “ei, ou > ē, ō when after y, w” could have both been valid at various points (as they seem to be in OP1), but lack of examples make this difficult to determine.

References ✧ PE19/106

Order (00400)

After 03700 AQ. [j], [w] often reduced between vowels
After 04200 AQ. [β], [ɣ] vocalized before voiced consonants

Related

Phonetic Rule Elements

[ei] > [ī] ✧ VT48/7 (ei > í)
[ou] > [ū] ✧ VT48/7 (ou > ū)

Phonetic Rule Examples

-eite > -īte ei > ī -iti > eiti > Q. íte ✧ PE22/155
keita- > kīta- ei > ī keye > {keit} > Q. kíta- ✧ VT49/19
lassei > lassī ei > ī lassḗi > lássei > Q. lassī ✧ PE19/106
lasseinen > lassīnen ei > ī AQ. lasséinen > lassēnen > Q. lassī́nen ✧ PE19/106
meinā > mīnā ei > ī meinā > Q. mína ✧ VT39/11
meinā > mīnā ei > ī meinā > Q. mína- ✧ VT39/11
lou > lū ou > ū LOW > lou > Q. ✧ PE17/137
loun > lūn ou > ū LOW > lounē̆ > Q. lūn ✧ PE17/137

ᴹQ. [ei], [ou] generally became [ī], [ū]; [ei|ou] > [ī|ū]

References ✧ Ety/WEY; PE19/53

Order (00400)

After 03800 ᴹAQ. [j], [w] often reduced between vowels

Related

Phonetic Rule Elements

[ei] > [ī] ✧ PE19/25 (ei > ī)
[ou] > [ū] ✧ PE19/25 (ou > ū)
[éi] > [ai] ✧ PE21/6 (ei > ai; after ı̯); Ety/WEY (weı̯ > waı̯); PE19/25 (ei > ai)
[óu] > [au] ✧ PE19/25 (ou > au)

Phonetic Rule Examples

ɣeiɣolosse > ɣīɣolosse ei > ī ᴹ✶Geı̯golosse > ᴹQ. Iolosse ✧ Ety/GEY
ɣeira > ɣīra ei > ī ᴹ√GEY > ᴹQ. íra ✧ Ety/GEY
ɣeire > ɣīre ei > ī ᴹ√GEY > ᴹQ. íre ✧ Ety/GEY
neire > nīre ei > ī ᴹ√NEI̯ > ᴹQ. níre ✧ Ety/NEI
neite > nīte ei > ī ᴹ✶neı̯ti- > ᴹQ. níte ✧ Ety/NEI
eira > aira éi > ai ᴹ√EY > ᴹQ. aira ✧ Ety/EY
eire > aire éi > ai ᴹ√EY > ᴹQ. aire ✧ Ety/EY
weire > waire éi > ai ᴹ✶weı̯rē > ᴹQ. Vaire ✧ Ety/WEY
nouθe > nauθe óu > au ᴹ✶nau̯þe > ᴹQ. nause ✧ Ety/NOWO

ᴱQ. [ei], [ou] became [ai], [au]; [ei|ou] > [ai|au]

Exception: neite

Order ()

After [ðʲ] became [j]
After 02600 [ji], [wu] became [i], [u] after a vowel
After 03400 [ou] became [u] before [e] and [o], but [o] before [i] and [a]
After 03700 intervocalic [ū], [ī] became [uw], [ij]

Phonetic Rule Elements

[ei] > [ai]
[ou] > [au]
[ēi] > [ei]

Phonetic Rule Examples

eika > aika ei > ai ᴱ√EI̯KA > ᴱQ. †aika ✧ QL/29
leika > laika ei > ai ᴱ√LAIKA > ᴱQ. laika ✧ QL/50
leiwa > laiwa ei > ai ᴱ✶sleiwa > ᴱQ. laiwa ✧ PE13/149
oule > aule ou > au ᴱ√OWO > ᴱQ. Aule ✧ QL/34
ouro > auro ou > au ᴱ✶ourū̆ > ᴱQ. auro ✧ PE13/155
loume > laume ou > au ᴱ✶Lou̯m > Laum > ᴱQ. laume ✧ QL/51
loure > laure ou > au ᴱ√LOU̯RI > ᴱQ. laure ✧ QL/51
souna > sauna ou > au ᴱ✶souna > ᴱQ. sauna ✧ PE13/148
soune > saune ou > au ᴱ√SOVO > ᴱQ. saune ✧ QL/86
sousa > sausa ou > au ᴱ√SOVO > ᴱQ. sausa ✧ QL/86
xoura > xaura ou > au ᴱ✶χou̯-ră > ᴱQ. haura ✧ GL/49
nēitte > neitte ēi > ei ᴱ✶nēgittĕ > ᴱQ. neite ✧ GL/60