► difficultnot easy to do, understand, or deal with:  His accent was difficult to understand. A lot of students find calculus difficult.
► hard making you tired because you have to use a lot of physical or mental effort:  Chopping wood is hard work. The midterms were harder than I expected.
► tough very difficult to do or deal with. Tough sounds more informal than difficult:  Doctors have to make tough decisions about who to treat first.
► awkward difficult to deal with or handle:  The big pieces of wood were awkward to carry.
► complicated/complex difficult to understand because of having a lot of different parts:  The rules of the game are very complicated.
► tricky informal complicated and full of problems:  The contract negotiations have been tricky.
► delicate needing to be dealt with carefully or sensitively in order to avoid problems or failure:  You must understand that this is a delicate situation, and I cannot discuss it publicly.
► challenging difficult in a way that is interesting and enjoyable:  The class is intended to be challenging for students.
► demanding difficult and needing a lot of time, effort, and skill. Used about jobs:  Being a nurse is a demanding job.
► daunting so difficult that you do not feel confident about being able to do it:  The task may seem a little daunting.
► formidable formal seeming very difficult and needing a lot of effort or skill to do:  The city still has a formidable problem of homelessness to deal with.
► grueling/arduous difficult and tiring and continuing for a long time:  The race is a grueling 24-hour run across the desert.
► laborious formal difficult and long and needing to be done very slowly and carefully:  Making a movie is a laborious process involving a huge amount of work.