The words 'have to' describe something that needs to take place soon. It expresses certainty, necessity, or obligation. 'have to'这个词是形容一些事即将要发生，它表达的是必然性、必要性或者义务。

Here are some examples: 这里有一些例子： 

"I have to switch schools." 

我必须要换个学校了。

"I have to use the telephone."

 我需要用电话。

"I have to go to the bathroom."

 我必须去洗手间。

"I have to leave."

 我必须离开了。

"I have to unpack my bags."

 我必须要打开我的袋子了。

You can also add the word 'don't' to suggest that someone is not required to do something. 你也可以加'don't'这个词来表示某人没有要求去做某事。

"I don't have to switch schools."

 我没必要换学校。

"I don't have to use the telephone."

 我不需要用电话。

"I don't have to go to the bathroom."

 我不需要用洗手间。

"I don't have to leave."

 我不需要马上离开。

"I don't have to unpack my bags."

 我不用打开我的袋子。