se (2), also long sé, preposition "at, in" (VT43:30; compare the "locative prefix" se- possibly occurring in an early "Qenya" text, VT27:25)
Quenya
-ssë
at
se
at, in
-on
-on
-n (3) a plural sign used in some of the case endings (WJ:407): Pl. genitive -on, pl. ablative -llon (but also -llor), pl. locative -ssen.
-ssë (1) locative ending (compare the preposition se, sé "at", q.v.); in Lóriendessë, lúmessë, máriessë, yalúmessë (q.v. for reference); pl. -ssen in yassen, lúmissen, mahalmassen, símaryassen, tarmenissen, q.v. Pronouns take the simple ending -ssë, even if the pronoun is plural by its meaning (messë "on us", VT44:12). The part. pl. (-lissë or -lissen) and dual (-tsë) locative endings are known from the Plotz letter only.