144　cannot，can not和can't含义相同，但用法上略有差别

① cannot原先只用于英式英语中，美式英语则分开写成can not，现在cannot则通用了。

You cannot leave now. It's raining hard outside. 你现在不能离开，外面正下大雨。

② can't为省略式，一般只用于口语中。

You can finish the work tomorrow，can't you？你明天能完成这项工作，对吗？

I can't go with you，Mary. 玛丽，我不能同你一起去。

③ can not分开写可以表示强调。

It is not a parking lot. You certainly can not park here. 这不是停车场，你绝不能在这里停车。