aux.用以构成完成式及完成式的不定式，表示已经…;
vt.有，具有; 拿，取得; 从事; 必须，不得不;
n.〈口〉有产者，有钱人; 富国; 〈英俚〉欺骗，诈骗;
助动词have以及它的变体has, had等的主要用法如下：
1. have +过去分词，构成完成时态。如：
He has left for Japan. 他已去了日本。
We’ve just done the washing-up. 我们刚洗完碗碟。
Poor Jim has just had an accident. 可怜的吉姆刚出了个事故。
I have had this car for three years. 这辆汽车我已用了3年了。
By the end of last month, they had finished the work. 上月未他们就已经完成了工作。
2. have + been +现在分词，构成完成进行时。如：
I have been studying English for 8 years. 我学英语已达八年了。
The children have been having a lot of run. 孩子们一直玩得很开心。
We had been doing business with each other for years before we quarreled. 在吵翻之前，我们多年来在业务上一直来往。
By this time next year, we will have been doing business with each other for 20 years. 到明年这时候，我们的业务住来就满20年了。
I woke up—I had been having a bad dream. 我醒了，我做了个噩梦。
3. have+been +过去分词，构成完成式被动语态。如：
English has been taught in China for many years. 中国教英语已经多年。
I have been made redundant, so I’m going abroad. 我被定成了超编人员，所以我打算出国。
Thousands of pounds have been spent on the new hospital. 这家新医院花费了数千英镑。
None of my friends have been invited to the party. 我的朋友中没有一个被邀参加晚会。
All means have been used to get him to change his mind. 为了转变他的想法，所有的办法都用过了
have 是动词原形i have,we have,you have,they have,to have...
has 是第三人称单数时用 he has,she has,it has
have用于第一人称（I,we),第二人称(you),及第三人称复数（they）；has用于第三人称单数（he,she,it)或单数名词.
1.否定句
主语+don't (doesn't)+have +….例：
We don't have any water here.我们这儿没有水.
This wall doesn't have a window in it.这面墙上没有一个窗户.
2.一般疑问句：
Do (Does)+主语+have+…?
肯定回答：Yes,主语+do (does).
否定回答：No,主语+don't (doesn't).例：
—Do you have a ruler?你有尺子吗?
—Yes,I do ./No,I don't.是的,我有./不,我没有.
—Does Lucy have a twin sister?露茜有个孪生姐姐吗?
—Yes,she does./No,she doesn't.是的,有./不,没有.
注意：do,does是助动词,do用于第一、二人称单、复数和第三人称复数；does用于第三人称单数形式.回答一般疑问句时,主语用人称代词表示；否定回答中don't或doesn't 一般不分开写.
注意：have (has)表示“有”时,一般不用于进行时态.
另外,在现代英语中,当“有”讲时,have/has的一般疑问句可以把have/has直接提前,当have/has作助词时表示完成时态时也可以直接提前.例：
They have a book.Have they a book?
3.“have”与“there be句型”的区别
have意为“有”,指所属关系；there be表示“某地有某物”,意指“存在”.例：
There's a book on the desk.桌子上有本书.
Xiao Wang has an English-Chinese dictionary.小王有本英汉字典.
动词have表示“有”，
位置就在主语后。
“三单”主语用has，
其他人称用have。
一般问句句首do/does添。
否定句子也一样，
don’t /doesn’t主语后面站。
1.A dog has four legs.
2.Our school has a library.
3.We have 37 chairs in our classroom.
4.My sister has a nice toy car.
5.Does that girl have a doll?
1 Alex has already gone
亚历克斯已经走了。
2 When I met her, she had just returned from a job interview
我遇见她时，她刚参加完一场求职面试回来。
3 You haven't sent her away, have you?
你还没有把她送走，是吗？
4 He arrived in San Francisco, having left New Jersey on January 19th
1月19日离开新泽西后，他到了旧金山。
5 I went out and had a walk around
我出去在周围散了一会儿步。