The semi-vowels [j], [w] frequently reduced between vowels, sometimes changing the preceding vowel in the process. The most common of these phonetic developments are ăya > ea and ăwa > oa, and similar sound changes were seen regularly from the 1910s through the 1960s. Among other things, these sound changes play a role in the history of verbal inflections in Quenya. For example, the present-tense suffix for weak verbs was -ea < -aya and the perfect suffix was -ie < -aye (PE17/77; PE22/159, 164).

The frequent reduction of intervocalic semi-vowels was a concept established quite early in Tolkien’s writings on Quenya, dating back to the Qenya Phonology of the 1910s. Two detailed descriptions of these developments have been published, one in the Qenya Phonology from the 1910s (PE12/11-13) and another in the Outline of Phonetic Development (OP1) from the 1940s (PE19/62-63), as well as more limited discussions scattered elsewhere in Tolkien’s writings.

In the 1910s the development of intervocalic semi-vowels depends primarily on stress patterns (PE12/11-13), but by the 1930s vowel length plays a greater role (PE19/62-63). In particular, if the preceding vowel was long, the semi-vowel was generally preserved:

After long vowels y, w remained and w was strengthened to TQ v. So māya, rāwa (rāva). In the case of māya there was a tendency to maiya, often represented in spelling maia, maiya (OP1, PE19/62).

The preserved y formed diphthongs with the preceding vowel, but preserved w remained and generally became v:

• ✶áyan [ājan] > aian “holy thing” (PE17/149).
• ✶máya [māja] > Maia (PE17/163).
• ✶wā-wā > váva “*wind” (PE17/34).
• ✶srāwe > hrávë “flesh” (MR/350).

After short vowels, however, the trend was towards semi-vowels weakening:

When [long vowels] unstressed and shortened the further changes occurred described below. After short vowels they [y, w] became weakened (OP1, PE19/62).

Intervocalic y tended to vanish after short ĭ/ĕ and intervocalic w after short ŭ/ŏ, but not necessarily after equivalent long vowels: see néya “once” vs. variant nea with short ĕ (VT49/31). Tolkien discussed this development in OP1 and elsewhere:

After ĭ, ŭ stressed or not (PQ accent) they [y, w] became very weak ı̯, u̯ glides and were seldom written. (Here w did not > v.) So manduwō > manduo. tŭwo > tuo. lĭye > lie (OP1, PE19/62).

ı̯ only to disappear after e, i; u̯ [after] o, u. aya > ea; awa > oa. w remains [?after] i, e. y [?after] o, u (from notes on verb inflections from the late 1960s, PE22/164).

Conversely, the semi-vowel y [ı̯] was generally preserved after ŏ/ŭ and w [u̯] after ĭ/ĕ, as indicated above. It seems y formed diphthongs in such cases and was represented as a vowel in writing, as was the case with y preserved after long vowels as noted above:

• Q. oialë [oı̯ale] “forever” < √OY (PE17/69).
• ᴹQ. tuia [tuı̯a] “sprouts, springs” < ᴹ√TUY (Ety/TUY).

However the w that remained after short ĕ/ĭ then developed into v as it did after long vowels: the development ewe > eve appears in a deleted note in OP1 (PE19/63 note #162). Furthermore, the semi-vowels could still be lost in these cases if y preceded e or w preceded o, such as: Q. eo “somebody” < ew + o (PM/340). This was also discussed by Tolkien in OP1:

In oya etc., ewa the y, w [was] usually preserved, but y van[ished] before e, w va[nished] before o, so ewo > ëo, oye > öe (OP1, PE19/63).

The most interesting developments occur for short ăy, ĕy and ăw, ŏw before vowels, including cases where the preceding vowel was originally long but became short in an unstressed position:

Short ăy, ĕy, ŏy; ăw, ŏw, ĕw had a special development. Similarly [for] unstressed ay, aw etc. < āy, āw. The y, w tended to be lost with or without modification of preceding vowel (OP1, PE19/62).

Here the trend was ăy- > e- before another vowel and ăw- > o- so that aya, ayo > ëa, ëo and awa, awe > öa, öe, where Tolkien used diereses in OP1 to explicitly mark the combinations as non-diphthongal. In the case of aye, awo > ë-e, ö-o, the vowels dissimilated to ie and uo, respectively, so that the result was aye, awo > ie, uo:

• aya, ayo, aye > ëa, ëo, ëe, the last ultimately > ie (OP1, PE19/63)
• awa, awe, awo > öa, öe, öo, the last ultimately > uo (OP1, PE19/63)

There is even evidence that awi > oi, as in ✶tawĭnā > Q. toina “wood” (PE17/115), so perhaps also ayu > eu (and eyu, owi > iu, ui; see below).

Likewise the tendency was ĕy- > i- and ŏw- > u- before vowels, just as the diphthongs [ei], [ou] generally became [ī], [ū]. Thus eye, eyo > ie, io and owe, owo > ue, uo (PE19/63). The developments given in OP1 before the vowel a were somewhat different: eya, owa > ëa, öa instead (PE19/63).

• eye, eyo, eya > ie, io, ëa (OP1, PE19/63)
• owe, owo, owa > ue, uo, öa (OP1, PE19/63)

The sound change owa > oa is consistent with known examples, but attested examples actually show eya > ia, contradicting OP1:

• ᴹQ. toa “woolen” < ᴹ√TOW (Ety/TOW).
• Q. pia “little” < √PEY (PE17/115).
• [deleted] ᴹQ. ia “ever” < ᴹ✶eı̯ā or ᴹ✶geiā (Ety/EY, GEY).

The only remaining combinations requiring discussion are Tolkien’s comments in OP1 (given above) that ŏy / ĕw also had special developments like ăy, ĕy / ăw, ŏw. Indeed, Tolkien began a chart with oya > oa and ewa > ea (PE19/63 note #162) before abandoning this idea, and replacing it with the quote given above (and repeated below):

In oya etc., ewa the y, w [was] usually preserved, but y van[ished] before e, w va[nished] before o, so ewo > ëo, oye > öe (OP1, PE19/63).

Thus the only special reductions of ŏy, ĕw were oye, ewo > oe, eo as discussed above (and probably also oyi, ewu > oi, eu). See contemporaneous ᴹQ. oiale “everlasting age” from The Etymologies (Ety/OY), not **oale.

In the 1940s and later, the interaction between stress and semi-vowel loss isn’t entirely clear. In OP1 Tolkien seems to indicate that the reductions only occur when the vowels were both short and unstressed: “When unstressed and shortened the further changes occurred described below” (PE19/62). However, this may refer only to long vowels that became short after being unstressed. There are definite examples of semi-vowel reduction after stressed short vowels:

• oantë < ✶áwa-n-tē, past tense of the verb auta- “to go away” (WJ/366).

However, in at least one place Tolkien gave this past tense as avante (PE17/63), so he may have sometimes conceived of stressed short vowels preventing semi-vowel reductions. Likewise, while it is clear that a preceding long vowel would prevent reduction, it is not clear whether this was also true of a following long vowel. The usual perfect of auta- was avánie < ✶a-wāniı̯ē (PE17/63, WJ/366), but Tolkien sometimes gave it as oávie < ✶a-wāwiı̯ē (PE17/148, PE22/164), which seems to indicate that semi-vowel reductions were possible even if the following vowel was long. This can also be seen in √SKEY [> skeyeite > skeyēte] > Q. xiéte “passing, impermanent” (PE22/155).

To summarize the full set of sound changes for intervocalic semi-vowels:

1. Semi-vowels were preserved after long vowels, with y [ı̯] forming diphthongs with the preceding vowel but w [u̯] developing into v.
2. Any w also survives before i (PE22/152) and probably also y before u.
   • @@@ counterexample: ✶tawĭnā > Q. toina “wood” (PE17/115).
3. y vanished after short ĭ/ĕ and w after short ŭ/ŏ.
4. y survived after short ŭ/ŏ and w after short ĭ/ĕ, developing as after long vowels (y diphthongizing and w > v) except:
   • oye, ewo > öe, ëo.
5. ăy-, ĕy- > e-, i- and ăw-, ŏw- > o-, u- except:
   • aye, awo > ëe, öo > ie, uo via dissimilation.
   • owa > öa (and eya > ëa in OP1, but > ia in most examples).
6. Preceding stress or a following long vowel may or may not have inhibited reduction (evidence is unclear).

Neo-Quenya: For Neo-Quenya, I think it’s simplest to assume stress doesn’t matter for semi-vowel reduction but a following long vowel will prevent it, just like a preceding long vowel. This gives the simplest explanation for the perfect avánie. Such long vowels in middle syllables would be rare in any case after long vowels shortened when the stress moved forward.

Conceptual Development: In the Qenya Phonology of the 1910s, semi-vowel preservation seems largely due to patterns of stress. In particular, whereas in the 1930s semi-vowels were preserved after long vowels, in the 1910s semi-vowels were generally preserved before stress, as indicated in the chart on PE12/13, for example: aiá, au̯á > ayá, awá. There is the caveat that y [ı̯] vanished after i/e and w [u̯] vanished after u/o, for example: eiá, ou̯á > eá, oá. There were some occasional aberrant developments whereby ei̯- > i-, ou̯- > u- even before a stressed vowel: ei̯é, ei̯ó, ei̯ú > ié, ió, iú (but not ei̯á) and ou̯é, ou̯ó, ou̯í > ué, uó, uí (but not ou̯á). However, the more regular results of ei̯é, ei̯ó, ei̯ú > eyé, eó, eú and ou̯ó, ou̯í > ovó, oí were given as alternates (but not ou̯é > oé; instead that alternate development was uá).

When stressed and short, we see special developments for ăy, ĕy and ăw, ŏw similar to those given in the 1930s for semi-vowels after short vowels, where ắı̯-, ĕ́ı̯- > e-, i- and ắu̯-, ŏ́u̯- > o-, u- (PE12/13):

• ắı̯a, ắı̯o, ắı̯u > ea, eo, eu
• ĕ́ı̯e, ĕ́ı̯o, ĕ́ı̯u > ie, io, iu
• ắu̯i, ắu̯a, ắu̯e > oi, oa, oe [the last later changing oe > oa]
• ŏ́u̯i, ŏ́u̯e, ŏ́u̯a, ŏ́u̯u > ui, ue, ua, uo

The 1930s dissimilations aye, awo > ë-e, ö-o > ie, uo did not occur: the results in the 1910s were either long ē, ō or preserved semi-vowels áye, áwo > aiye, ávo. Furthermore, there are many variants where ắı̯-, ĕ́ı̯- > aiy-, e- and ắu̯-, ŏ́u̯- > av-, u- instead of e-, i-; o-, u-. This includes several alternate forms of the above (marked with *):

• ắı̯i, ắı̯o, ắı̯u > ai, aiyo*, aiyu*
• ĕ́ı̯a, ĕ́ı̯o, ĕ́ı̯u > ea, eo*, eu*
• ắu̯i, ắu̯e > ávi*, ávo [perhaps a slip for áve?]
• ŏ́u̯i, ŏ́u̯a, ŏ́u̯e > oi*, oa*, oa* [the last presumably ŏ́u̯e > oe > oa, see above]

Given the large number of variant developments and the lack of clear examples in the 1910s, Tolkien’s precise ideas are hard to decipher, but there are clear indications of the later system already in Tolkien’s earliest writings.

@@@ counterexample: ua (GL/61)