彼の声は単調で、聞いていると眠くなる。
His voice is so monotonous that listening to him makes me sleepy.
毎日同じことの繰り返しで、生活が単調になってきた。
Doing the same thing every day, my life has become monotonous.
この曲はメロディーが単調だが、不思議と心に残る。
The melody of this song is simple and unvaried, yet it strangely stays with you.
単調な作業が何時間も続いた。
The tedious work went on for hours.