(no distinct pl. form).
Noldorin
ennin
noun. Valian year
idhrin
noun. year
idhrind
noun. year
în
noun. year
în
noun. year
Sindarin
idhrinn
noun. year
în
noun. year
idhrinn
year
în
year
- în, no distinct pl. form; coll. pl. ?íniath. 2) idhrinn (no distinct pl. form). LONG YEAR (Valian year) ennin. No distinct pl. form, but coll. pl. enniniath.
în
year
no distinct pl. form; coll. pl. ?íniath.
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
Early Quenya
lúmen
noun. year, period
latta
noun. year
Gnomish
fann
noun. year
fanuin
masculine name. Year
lath
noun. year
Qenya
loa
noun. year
yén
noun. year
Middle Primitive Elvish
yen
root. year
A root in The Etymologies of the 1930s glossed “year” with derivatives like ᴹQ. yén/N. în “year” (Ety/YEN). Tolkien’s ongoing use of words like Q. yén and S. ínias “annals” indicate its ongoing validity (LotR/377; MR/200), but in Quenya at least the meaning shifted to that of an “Elvish long year”, equal to 144 solar years (LotR/1107; MR/471; NM/84).
yenrinde
noun. year
A Sindarin word for “year”, derived from the primitive root ᴹ√YEN of similar meaning, with its vowel sound the result of [[s|a long [ē] becoming [ī]]].
Conceptual Development: The word în first appeared in The Etymologies from the 1930s with the gloss and derivation given above. It did not directly appear in Tolkien’s later writings, but was an element in several later words such as S. ínias “annals” and S. ifant “aged” (lit. “year full”). Furthermore, its Quenya cognate yén did reappear in the Lord of the Rings appendices.
In The Etymologies, both N. în and ᴹQ. yén were glossed “year”, and there were other words for longer periods of time, such as ᴹQ. qantien “century, (lit.) full year” and N. anrand “cycle, age”. In the Lord of the Rings and other later writings, Tolkien changed the meaning Q. yén to an “Elvish century” of 144 years. It is quite likely that S. în also changed to this meaning, but since it did not appear as an independent word in later writing, we have no direct confirmation of this.
Neo-Sindarin: Most Neo-Sindarin writers continue to use în with the sense “year” (that is, a solar year of 365 days). If you are concerned with this word’s true meaning, you might instead use a neologism for this period of time, such as ᴺS. lóran or ᴺS. coranor, but since these are not in widespread use, it is less likely a reader would understand your meaning.