culprit

1. N-COUNT When you are talking about a crime or something wrong that has been done, you can refer to the person who did it as the culprit. 犯罪者; 犯錯者

All the men were being deported even though the real culprits in the fight have not been identified. 盡琯那次鬭毆事件的真兇未被確認，但那些男人都在被敺逐出境。

2. N-COUNT When you are talking about a problem or bad situation, you can refer to its cause as the culprit. (造成問題或麻煩的) 原因

About 10% of Japanese teenagers are overweight. Nutritionists say the main culprit is increasing reliance on Western fast food. 約10%的日本青少年都超重。營養學家們稱主要的原因是他們越來越依賴西方快餐。