A word for “darkness” or “blackness” appear in the Namárië, a noun form of morna “black, dark” (LotR/377; PE17/73).
Quenya
mornië
darkness
mornië
noun. darkness, blackness
ar sindanóriello mornië caita
and from a grey country darkness lies
The 12th phrase of the prose Namárië. Tolkien altered the text from the poetic version as follows:
> ar sindanóriello caita mornië >> ar sindanóriello mornië caita
Tolkien simply moved the subject mornië “darkness” before the verb caita “lies” to be consistent with the usual Quenya subject-verb-object word order.
mor
darkness
mor noun "darkness" (Letters:308; probably just an Elvish "element" rather than a complete word; Namárië has mornië for "darkness")
lúmë
noun. darkness
A noun in the 1960s versions of the Markirya glossed “darkness” (MC/222), perhaps derived from a root √DU as suggested by David Salo in a post to the Elfling mailing list in 2012 (Elfling/362.96).
Neo-Quenya: I’d generally use Q. huinë for “darkness” in Neo-Quenya, but that word is more for total darkness, whereas lúmë might be a less severe form of darkness, a variant of Q. lómë “night, dusk”.
ar sindanóriello caita mornië
and out of a grey country darkness lies
Twelth line @@@
lúmë
darkness
lúmë (2) noun "darkness" (one wonders if Tolkien confused lúmë "time, hour" and lómë "night") (Markirya)
mornië noun "darkness" (Nam, RGEO:67), "dark, blackness" (PE17:73). Early "Qenya" also has Mornië "Black Grief", "the black ship that plies between Mandos and Erumáni" (LT1:261). This is probably a compound of mor- "black" and nië "tear".