while和when什么情况下可以互换

While 后面跟的从句里的动作是正在进行时 he comes home while his mother is cooking.when就不是了 he comes home when his mother cooks.非常感谢哟！想再请问下when/while she was visiting the museum, an alien came in. 这个位置互换的理由是什么呢当从句的谓语是表动作的延续性动词时，when, while才有可能互相替代。如：While / When we were still laughing, the teacher came in.正当我们仍在大声嬉笑时，老师进来了。