Quenya 

ú-

verb. not-, un-, in-

ú- (2) prefix "not-, un-, in-", denying presence or possession of thing or quality (VT39:14, UGU/UMU/VT46:20, GŪ, LT1:272), or simply suggesting something bad or immoral (see #úcar-, Úmaiar). Tolkien at one point considered redefining ú- as an element signifying "bad, uneasy, hard"; the already-published form únótima would then mean "difficult/impossible to count" rather than simply "uncountable" (VT42:33). However, Tolkien's very last word on the matter seems to be that ú- was to remain a mere negative (VT44:4). Compare úa, q.v. According to the Etymologies, the prefix ú- usually has a "bad sense", whereas according to early material u- (uv-, um-, un-) is a "mere negation" (UGU/UMU vs. VT42:32) According to a later source, ú- could be used as an uninflected verbal prefix, mainly in verse, but in a normal style the prefix was "verbalized" as ua-, q.v. (PE17:144). The stem Ū, as a negation, was accompanied by "pursed lips and shaking of the head" (PE17:145).