People don't seem to like Thanissaro Bhikkhu's translation to "stress," but he gives a few reasons why he uses it instead of suffering. First, as Bhikkhu Pesala pointed out, dukkha is too specific. Stress can be in any kind of activity, including the most sublime and blissful states of meditation - something which people would hardly describe as "suffering." The other main reason was that "stress" is harder to romanticize than suffering. People claim to suffer for this or that reason (love, art, whatever), or attribute some sort of nobility to their suffering, but you never hear anybody talk about "my noble stress."
In the "Pali Word a Day" from Buddhanet.net (http://www.buddhanet.net/pdf_file/paliwordday.pdf
) they break down dukkha as du = difficult / +kha (to endure)
But "du" and "kha" don't seem to translate quite that way when I try it in the online PTS pali dictionary.Du
Du3 ( -- ˚) (adj. -- suff.) [Sk. druha, druh, see duhana & duhitika] hurting, injuring, acting perfidiously, betraying, only in mitta˚ deceiving one's friends S i.225; Sn 244 expl. as mitta -- dūbhaka SnA 287, v. l. B mittadussaka; cp. mitta -- dubbhika & mitta -- dubbhin.Kha
Kha syllable & ending, functioning also as root, meaning "void, empty" or as n. meaning "space"; expld. by Bdhgh with ref. to dukkha as "khaŋ saddo pana tucche; tucchaŋ hi ākāsaŋ khan ti vuccati" Vism 494. -- In meaning "space, sky" in cpd. khaga "sky -- goer" (cp. viha -- ga of same meaning), i. e. bird Abhp 624; Bdhd 56