What is another word for "problem"?

Roget's Thesaurus (1911) lists these synonyms for "problem": accede, accept, acceptance, accession, acknowledge, acknowledgment, acquiesce, acquiescence, adjustment, admit, agnition, agnize, agree, agreement, all, allow, anagram, and, approval, arcanum, assent, book, charade, close, come, compliance, comply, concealed, concede, concession, confidential, confirmation, consent, conundrum, course, crack, crux, dead, deign, difficulty.