weariness or languor — a prolonged physical or mental fatigue or lack of motivation (often used as 倦怠感).
長時間の残業で倦怠感が取れない。
I can't shake off the sense of fatigue after working long overtime hours.
慢性的な疲労や倦怠に悩む人が増えている。
The number of people suffering from chronic fatigue and weariness is increasing.
単調な仕事に倦怠を感じ始めた。
I've begun to feel bored and weary of the monotonous work.