Early Primitive Elvish
leŋe
root. LEŊE
lene
root. long
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 root in the Qenya Lexicon of the 1910s given as ᴱ√LENE “long”, with the added explanation that it “developed in opp. directions of slow, tedious, trailing, etc. and - stretch, thin, etc.”. Tolkien originally put the word ᴱQ. lenka “slow, left” under this root, but seems to have transferred this word to ᴱ√LEKE, perhaps at the same time he elaborated on the meaning of ᴱ√LENE “long”. Its remaining derivatives include ᴱQ. lenwa “long and thin, straight, narrow” and ᴱQ. lenu- “stretch”.
There are a number of words in the Gnomish Lexicon that seem to be derived from this root, including G. len “wherewith, far, long, away” and G. lenwi “length, distance”, but these were rejected, and Tolkien replaced them with G. lenc “far, distant” derived from ᴱ√leŋe (which was followed by other similar Gnomish derivatives), possibly representing a conceptual shift in this root (GL/53). In any case, there are no clear signs of this root in Tolkien’s later writing, unless perhaps it remanifested as ᴹ√LEN “way, (?road)” from The Etymologies of the 1930s (EtyAC/LEN).