Psychological or physical pressure or tension experienced as strain; the unpleasant effects (mental or physical) caused by such pressure, often from work, relationships, etc.
最近は仕事のストレスでよく眠れない。
Lately I haven't been able to sleep well because of work stress.
適度な運動はストレス解消に効果がある。
Moderate exercise is effective for relieving stress.
彼はストレスが原因で頭痛がするらしい。
It seems he has headaches caused by stress.