通常理解isn't为否定的意思或“不是”。isn't=is not，是is not的用法和缩写经常用在反义疑问句里，反义疑问句起强调作用，没有不礼貌的问题。

双语例句

1.It isn't too difficult once you get the idea.

你一旦弄懂了，就不太难了。

2.'That's crazy,' I said. 'Isn't it just?' he said.

“那简直是疯了，”我说。“谁说不是呢？”他说。

3.Perhaps he isn't coming.

他许不来了。

4.It's past the appointed time. Maybe he isn't coming.

约定的时间都过了，别是他不来了吧？

5.Isn't that enough for you?

那对你来说不够吗？