所谓插入语指的是对一句话所做的附加的解释。最常见的插入语有：

1. That will be a good beginning, I hope.

2. We'll have to take an umbrella, I' m afraid.

3. I have no money, you see.

4. He is a bad guy, you know.

5. Mr. Smith, I think, is at least 50 years old.

6. This, I suppose, will give you some idea of the situation in China.

I think 如果放在句子中间将句子断开，或是放在句末，就是插入语。如果放在句首，就不是，而是一个主句。如：I think he will help you. 在这句话中，主句是I think；从句是he will help you.