単調

(1)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"

(2)退屈なほど不変で変化に乏しい性質

(3)an unchanging intonation

(4)変化のないイントネーション