s nouns the difference between cinema and theater is that cinema is (countable) a film while theater is a place or building, consisting of a stage and seating, in which an audience gathers to watch plays, musical performances, public ceremonies, and so on.
作为名词，cinema和theater的区别在于cinema(可数名词)可以指电影，而theater则指一个地方或建筑，它由舞台和座位组成，观众可以聚集在那里观看戏剧、音乐表演、公共仪式等。
They can mean exactly the same thing: Americans go to the theater to watch a movie. The British go to the cinema to watch a film.
他们也可以指一回事：美国人去theater看电影，而英国人则到cinema看电影。
But no AmE speaker uses "going to the cinema" to mean "going to the movies" unless that person is joking (possibly while assuming a fake British accent) or horribly pretentious.
但是美国人没有人用“going to the cinema”来指“去电影院”的，除非你在开玩笑（可能是想模仿英式口音）或者装腔作势。
In both countries, "theater" (US spelling) (and "theatre", UK spelling) means a place where you go to watch stage plays.
在这两个国家，当指可以看舞台剧的“剧院”时，都是说“theater”。