soron (or sornë) (þ) noun "eagle", before an ending sorn- as in pl. sorni, "gen.sg....sornen"; in LotR-style Quenya this would be the dative singular instead (THOR/THORON). SD:290 has the pl.soroni "eagles", changed to sorni as in the Etymologies. Early "Qenya" has the forms sor, sornë (LT1:266)
Quenya
soron
noun. eagle
soron
eagle
soronto
masculine name. Soronto
sorontar
masculine name. King of Eagles
The Quenya name of Thorondor, a compound of the prefixal form soron- of soron “eagle” and the word element -tar “king” used in compounds (SA/thoron; Ety/TĀ, THOR).
Conceptual Development: In the earliest Lost Tales, this character’s name once appeared as ᴱQ. Ramandur (LT2/203) but in this instance it was replaced by ᴱQ. Sorontur “King of Eagles”, which was his usual Qenya name in the early stories (LT1/73, LT2/192). His name appeared in The Etymologies from the 1930s as ᴹQ. Sorontar “King of Eagles”, and these entries are the source for the etymology given above (Ety/TĀ, THOR). This name appeared in Silmarillion revisions and notes from the 1950s (MR/410, WJ/272) and also in The Silmarillion appendix (SA/thoron), but Christopher Tolkien did not include it in the main text of the published version of The Silmarillion.
sorontil
place name. Eagle-horn
A mountain by the sea in Númenor which was “the abode of many eagles” (UT/167). Christopher Tolkien translated the name as “Eagle-horn” (UTI/Sorontil), and it is likely a compound of the prefixal form soron- of soron “eagle” and the word tildë “point” also seen in Taniquetil. If so, the stem form of this name was probably Sorontild-.
soronúmë
proper name. *Eagle of the West
soronildi
proper name. Eorlingas
Soronto
eagle
Soronto (þ?), masc. name, seems to incorporate soron "eagle"; the ending -to is rare (occurs in suhto, q.v.), here apparently used to derive a masculine name.
Soronúmë
eagle
Soronúmë (prob. þ) (name of a constellation, apparently incorporating soron "eagle") (SA:thoron)
sorno
eagle
sorno (þ) noun "eagle" (archaic thorno) _(Letters:427). Also soron. Early "Qenya" has sor, sornë (LT1:266)_
Sorontar
king of eagles
Sorontar (þ) masc. name "King of Eagles", Sindarin Thorondor, name of a great Eagle (SA:thoron, THOR/THORON, TĀ/TA3)
Soronildi
name. Eorlingas
sorno
noun. eagle
sor
eagle
sor, sornë noun "eagle" (LT1:266); rather soron in LotR-style Quenya
ëa
eagle
ëa (3) "eagle" (LT1:251, LT2:338), a "Qenya" word apparently superseded by soron, sornë in Tolkien's later forms of Quenya.
ëaren
eagle
ëaren noun "eagle" or "eyrie" (LT1:251; this early "Qenya" word is evidently no more valid than ëa "eagle" in LotR-style Quenya.)
The Quenya word for “eagle”, appearing in a number of compounds, derived from primitive ✶thorono and the root ᴹ√THOR(ON) “come swooping down” (PE22/159; Let/427; Ety/THOR; PE21/33). It had couple variants such as sorno (Let/427) and sorne (Ety/THOR), but consistently appeared as soron- in compounds. Its stem form isn’t entirely clear: its most common plural form was sorni (Ety/THOR; SD/290), which is the expected result from the Quenya syncope, but in one place it had the plural soroni and the presence of the variant sorne muddies the waters.
Conceptual Development: This word appeared as ᴱQ. sorne or sor (sorn-) “eagle” in the Qenya Lexicon of the 1910s derived from the early root ᴱ√ŠORO [ÞORO] (QL/86). The form sorn- “eagle” also appeared in the Poetic and Mythological Words of Eldarissa where Tolkien indicated the primitive form was sorni- (PME/86). The form ᴱQ. soron appeared in Early Noldorin Word-lists of the 1920s as a cognate of ᴱN. thorn “eagle” (PE13/154), and Tolkien mostly stuck with that form thereafter, though he occasionally used variants like sorne and sorno as noted above.
In the Declension of Nouns from the early 1930s, Tolkien listed a large number of declined forms for ᴹQ. soron “eagle”, and those declensions used soron- (or sorun-) as their base. In The Etymologies of the 1930s, however, Tolkien gave plural sorni and genitive sornen indicating a stem form sorn-, but that document also gave sorne as an alternate form of soron “eagle”. Nevertheless, I think from the 1930s forward, it is more likely that Quenya syncope would have come into play in the declension of this word, so it would have plural sorni, dative sornen, ablative sornello, etc. The only noun case where the primitive stem would be preserved would be possessive soronwa.