il- (prefix) "no, *un-" (LA); cf. ilfirin "immortal" (vs. firin "dead"). This prefix "denotes the opposite, the reversal, i.e. more than the mere negation" (VT42:32). But il- can also mean "all, every"; see ilaurëa, ilqua, ilquen.
Quenya
la
no, not
il-
verb. no, *un-
lá
no, not
lá (1) adv. "no, not" (LA, VT45:25) According to VT42:33, lá is the stressed form, alternating with la when the negation is unstressed. In another conceptual phase of Tolkien's, lá had the opposite meaning "yes" (VT42:32-33), but this idea is contradicted by both earlier and later material: usually lá is conceived as a negation. The negation can receive tense markers and be used as a negative verb "when [another] verb is not expressed" (VT49:13), apparently where the phrase "is not" is followed by a noun or an adjective as a predicate, or where some verb is understood, as in English "I do not" (i.e. "I do not do whatever the context indicates"). With pronominal endings la- in the aorist, e.g. lanyë "I do not, am not" (etc.) (Tolkien abandoned the form lamin.) Exemplified in the sentence melin sé apa lanyë hé *"I love him but I do not [love] him" (another person) (VT49:15). Present tense laia, past lánë, perfect alaië, future lauva.
ui
no
ui interjection "no" (originally an endingless negative verb in the 3rd person aorist: "it is not [so]"; see #u-). Apparently this is the word for "no" used to deny that something is true (compare vá, which is rather used to reject orders, or to issue negative orders). (VT49:28) Compare uito.
la negation "no, not" (see lá); also prefix la- as in lacarë, q.v. (VT45:25)