monotony, humdrum, sameness -- (the quality of wearisome constancy, routine, and lack of variety; "he had never grown accustomed to the monotony of his work"; "he was sick of the humdrum of his fellow prisoners"; "he hated the sameness of the food the college served")
humdrum, monotonous -- (tediously repetitious or lacking in variety; "a humdrum existence; all work and no play"; "nothing is so monotonous as the sea")