憂鬱
ゆううつ · yuuutsu · JLPT N1 · noun
melancholy
憂 (yū, worry) + 鬱 (utsu, gloom): worry that settles in like heavy fog.
Both characters carry a sense of heaviness: 憂 is worry and 鬱 is a stagnant, clouded state. Together they name a low mood that weighs on a person for a long time.