"困"用英语可以说作"tired"，它来源于中文词汇。
例句：
I'm so tired. (我好困。)
She was tired from working all day. (她因为整天工作而感到疲倦。)
The long fpght made him feel tired. (长途飞行使他感到疲倦。)
请注意,在英语中还有其他形容疲倦的词汇，如：exhausted, fatigued, worn out。
例句：
He was exhausted after running a marathon. (他在跑马拉松后感到筋疲力尽。)
She was fatigued from the long hike. (她因为长途徒步旅行而感到疲乏。)
I'm worn out from all the stress. (我因为所有的压力而感到疲倦。)