たんちょう単調tanchou
1.

Describing a state or experience that lacks variety or change, often leading to boredom or a sense of dullness in activities or routines.

2.

Characterizing something that maintains a consistent and unvarying pattern, resulting in a feeling of uniformity and absence of excitement.

3.

Referring to a quality of sound or rhythm that does not contain variation, producing a flat or uninteresting auditory experience.

Example:

この話はちょっと単調だ。