1.做动词vt,意为：有
例如：我有一本书
I have a book.
2.吃午饭 have a lunch 喝茶 have a cup of tea
3.have to 意为：不得不
例如：今天是星期一,我必须去上学.
Today is Monday,I have togo to school.
4.have+动词的过去分词,构成现在完成时.表示过去某一段时间发生的事情对现在造成的影响.
例如：昨天女儿生病了,我必须留在家里照看她
My daughter was ill yesterday,so I have left to take care of her.