Gnomish
laith
noun. time, the course of time; (properly) lapse
laith(r)a-
verb. to let slip, lose, mislay, forget; (intr.) to be lost
aluin
masculine name. Time
lûm
noun. time
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A verb appearing as G. laitha- or laithra- “let slip, lose, mislay, forget” from the Gnomish Lexicon; it could also be used intransitively to mean “to be lost”, especially in the form laithra- (GL/52). Tolkien said it was the result of a mingling of two roots: ᴱ√lech and ᴱ√lith-, the former having to do with slippery things and the latter with time.
Neo-Sindarin: In 2018 I made an attempt to salvage this verb (my suggestion was ᴺS. laetha-), but this was rejected by the community. In a Discord conversation in 2022-04-16, Elaran proposed redefining this verb as lítha- “to let slip, lose, mislay; (intr.) to be lost” based on the later root √LIK “slip” which was recently published; by extension it can also mean “to forget”. I quickly adopted Elaran’s proposal as better than mine.