Middle Primitive Elvish
phuine
noun. night, deep shadow, nightshade
doʒ
root. night
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 Etymologies of the 1930s glossed “night” that (along with ᴹ√DOM) was the basis for the ᴹQ. lóme/N. dû “night” (Ety/DOƷ). It replaced some rejected variants ᴹ√LOƷ and ᴹ√DAW (EtyAC/LOƷ). Many of the derivatives of ᴹ√DOƷ were later assigned to other roots: N. dûr “dark” became S. dûr “dark” < √NDU “under, down” in notes from the late 1950s or early 1960s (PE17/152) and ᴹQ. lóna “dark” became Q. lúna (PE17/22). There are no signs of ᴹQ. ló “night” and N. daw “night-time, gloom” in Tolkien’s later writing. Future derivations of Q. lómë/S. dû only mention the root √DOM (PE17/152; PE22/153) and thus ᴹ√DOƷ may have been abandoned.
In a message to the Elfling mailing list from July 2012 (Elfling/362.96), David Salo suggested there might be a later root ✱√DU serving as the basis for Q. lúna “dark” and Q. lúmë “darkness”, though the latter might instead be from √LUM. Such a root ✱√DU is not attested in Tolkien’s writings, but if it existed, it could be a later iteration of ᴹ√DOƷ. Another possible example of the root ✱√DU is primitive ✶durnŭ “dark of hue”.