-nenmost nouns have an instrumental in -nen
-nen instrumental ending (pl. -inen, dual -nten, partitive pl. -línen). Attested in ambartanen, lírinen, lintieryanen, súrinen, parmanen; see ambar (#2), lírë, lintië, súrë, parma. Tolkien noted that "most nouns have an instrumental in -nen" (PE17:62), a wording suggesting that the form of the ending may vary; given the normal development ln > ld, it is possible that it would appear as *-den when added to a noun in -l (*macilden "with a sword").
nén (nen-) noun "water" (NEN).
Uinen (Uinend-, as in dative Uinenden) fem. name, used of a Maia, spouse of Ossë (UY, NEN). Adopted and adapted from Valarin (WJ:404), though it is also said that it contains -nen "water" (SA:nen); the latter explanation may be folk etymology. In the Etymologies, the name is derived from the same stem (UY) as uilë "long trailing plant, especially seaweed".
Nénar noun name of a star (or planet), evidently derived from nén "water" (Silm), tentatively identified with Uranus (MR:435)
lintië noun "swiftness, speed" derived from linta; also used as adverb "quickly", nornë lintië "he ran with swiftness", also more explicitly with pronominal suffixes and the instrumental ending -nen: lintieryanen "with his speed" (PE17:58)