at night习惯上的固定搭配，侧重于晚上，只能是“在夜里/间”，比in the evening 稍微要迟一些。 in the evening,比较侧重于傍晚那段时间，可以指“在黄昏”,in the evening可用于一般将来时或一般现在时，at night可用于一般过去时。
in the evening的用法举例
in the evening是“在傍晚、晚上”，表示的在当天或者在某一天的晚上，用于一般将来时或一般现在时。
例句：My mother needs me by her side in the evening.我母亲晚上需要我陪在她身边。
Do you always go out for a walk in the evening?你晚上总去散步吗？
Supper is from 5.00 to 6.00 in the evening.晚餐在傍晚5点到6点之间。
He finishes his homework at eight o'clock in the evening.他在晚上8点完成作业。
They worked without a break until about nine in the evening. 他们一刻不停地干到晚上九点钟左右。
In the evening the general manager g***e a banquet at the international hotel in honour of the foreign guests.当晚总经理设座国际饭店宴请外宾。
in the evening不具体的晚上，可用作可数名词，也可用作不可数名词。
I will go to the cinema with my sister in the evening. 我晚上会和姐姐去电影院。
I go to the cinema with my sister in the evenings. 我每个晚上会和姐姐去电影院。
at night用法举例
at night指夜晚，通常表泛指，可用于一般现在时，还可用于一般过去时。
例句：Thieves broke into my home at night.小偷晚上闯进了我家。
I don't watch Tv late at night.我深夜不看电视。
It was late at night and Mary was still working away at his homework.夜深了，玛丽还在做课外作业。
I had to work late at night.我不得不深夜工作。
I don't finsh my homework late at night. 我深夜不完成作业。
