arduous

/ˈär-jə-wəs/

Latin arduus high, steep, difficult; akin to Old Irish ard high

adjective

  1. hard to accomplish or achieve : difficult

  2. marked by great labor or effort : strenuous

  3. hard to climb : steep

an arduous task

… a life of arduous toil.

hard difficult arduous mean demanding great exertion or effort. hard implies the opposite of all that is easy. difficult implies the presence of obstacles to be surmounted or puzzles to be resolved and suggests the need of skill or courage.