is not的縮寫形式是isn't。縮寫是寫作教程中的重要組成部分。是為便利使用，由較長的語詞縮短省略而成的語詞。

含有 am is are的時候，使用縮寫形式

如：I'm=I am；she's=she is；he's=he is；it's=it is；we're =we are；you're =you are；they're=they are；there're=there are；that's=that is；Sam's=Sam is

含有have，has以及他們的過去式had的時候，常用縮寫式

如：Weve got=we have got；You've got=you have got；they've got=they have got；she's got=she has got；he's got=he has got；it's got=it has got

含有not的時候，常用縮寫形式

如：isn't=is not；aren't=are not；can't=can not；that's=that not；let's=let is；my name's=my name is

含有 would/ should/had l的時候，常用縮寫形式

如：I'd=I would/should/had；You'd=You would/should/had；We'd=We would/should/had

過去時態(tài)否定形式的縮寫

如：wasn't=was not；weren't were not