sarda adj. "hard" (VT39:17); pl. sardë "hards" may be used in the same sense as sarda tengwi, q.v. (As an independent form we would rather expect a nominal pl. sardar.)
Quenya
ur(u)-
prefix. hard, difficult, difficult, hard
sarda
hard
torna
hard
#torna adj. "hard", as in tornanga (q.v.), seemingly -storna after prefixes ending in a vowel, as in the comparative forms aristorna, anastorna (PE17:56; the forms are untranslated and may not necessarily be the same adjective "hard".)
torna
adjective. hard
urda
hard, difficult, arduous
urda adj. "hard, difficult, arduous" (PE17:154)
A prefix appearing in Definitive Linguistic Notes (DLN) from 1959, meaning “hard, difficult” based on the root √GUR of similar meaning (PE17/154). Tolkien gave as examples of its use: urucarin “made with difficulty” and urcarne or urucárima “hard to make / do”.
Conceptual Development: On a rejected draft page Tolkien also had an unglossed prefixal form ur- apparently derived from √GUR “hard, stiff, difficult, cumbrous, slow”, with an unglossed example urunóte or urnótima, likely “✱difficult to count” (PE17/172). On this same rejected page Tolkien had ur(u) based on √UTHU “unsuitable, bad, improper, useless, wrong”, but since this derivation doesn’t make sense this is probably a slip or misreading for the prefix us-; see that entry for discussion.
Neo-Quenya: I believe that ur(u)- has the connotation “difficult, arduous” due to the inherent complexity of the task, as opposed to hrai- meaning “difficult, hard” due to resistance from the thing or people being worked upon.