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"
Adjective:
not challenging; dull and lacking excitement;
"an unglamorous job greasing engines"
tediously repetitious or lacking in variety;
"a humdrum existence; all work and no play" "nothing is so monotonous as the sea"
