a matter or situation regarded as unwelcome or harmful and needing to be dealt with and overcome.
they have financial problems
同义词：
difficultyissuetroubleworrycomplicationdifficult situationmessmuddlemix-upsnaghitchdrawbackstumbling blockobstaclehurdlehiccupsetbackcatchcatch-22vexed questionquandarythe rubpredicamentplightcan of wormshornets' nestGordian knotmisfortunemishapmisadventurenuisancesource of difficultybotherpestsource of troubleirritantthorn in one's side/fleshvexationinformal：dilemmaheadacheprobhasslepicklefixtight spotfly in the ointmenthow-do-you-dojobgremlinfacerkatzenjammerrare：nodusinformal：dragpainpain in the neckfair cow
2
Physics
an inquiry starting from given conditions to investigate or demonstrate a fact, result, or law.
