Question

in summer和in the summer有什么区别

Answer 1

in summer和in the summer的区别是泛指和特指的区别。
in summer就是一般的在夏天里，没有特别说明是今年的夏天还是过去的夏天，是泛指。例如：
We like swimming in summer.夏天我们喜欢游泳。

in the summer是特指某一个夏天。
In the summer of 1980,a patient had a strange purp lish spot removed from below his ear.1980年的复天，一名患者将一颗略带紫色的斑点从其耳下处移除。

Answer 2

in summer指的是抽象的夏天.

比如:Most people like to swim in summer, but some are fond of swimming in winter.大多数人喜欢夏天游泳,有些人喜欢冬天游.

in the summer指某个特定的夏天.比如:

I will go to Tibet in the summer.

为了强调也会说“in this summer”,不过人们更习惯省掉in.

Answer 3

in summer 只是单纯指在夏天
而in the summer 往往接一个限定词，表示在...的一个夏天 ，比如：
in the summer of 1996
in the summer of a misery year