关键词3：have to

情态动词have to （口语中说成have got to） 表示客观需要做的事情，意为“必须；不得不”(也就是客观条件强迫主语必须得这样做，没有商量的余地，预期比较强硬)。 1 have to同情态动词must 的区别。have to 和must 都有“必须”的意思。但是 have to侧重于强调客观条件需要做的事情。而must 侧重于表示说话人的主观看法，认为有义务，有必要去做某事。例如： I have to clean my room first. You must be here before eight. 2 have to 有人称和数的变化，其他情态动词没有。例如： Mr lee has to work on the farm all day long. You /I can go swimming this Sunday3 have to有多种时态的变化，而can, may等只有过去式等形式。例如： We will have to finish it the day after tomorrow I thought I could sell something used4 have to不能直接用来否定或提问，需要助动词do / did / does等帮助。而其他的情态动词一般都可以直接进行否定和提问。

例如： Where do I have to go? May I come in?
You don/'t have to help her with her English =you don’t need to help her with her English 5 have to可以被may 等情态动词修饰，其他动词之间不能互相修饰。例如： I think you may have to finish the work today.
重点动词have 1：实义动词，本身包含具体的词意"有"，I have a computer
否定句 :主语+do/does/did+not+have+其他=主语+have/has/had+not+其他
例如：I do not have a computer=I have not a computer
疑问句：Have/has/had+主语+其他=Do/does/did +主语+have+其他？
Have you a computer?=Do you have a computer?

2 Have 助动词have/has/had+done构成完成时
肯定句：主语+have/has/had+过去分词+其他 I have finished my work.
否定句：主语+have/has/had+not+过去分词+其他 I have not finished my work
疑问句：Have/has/had+主语+过去分词+其他？Have you finished your work?

3 have还可以和很多单词，特别是那些既是动词又是名词的词连用，构成很多短语，其词意则是由与其连用的词语来决定，它的活跃之处也就在于此。例如： have a talk 谈话 have a tea 喝茶 have a rest 休息一会儿 have a class 上课 have a hike 远足 have a picnic 野炊 have a concert 举办音乐会 have a visit 参观；访问 have a look 瞧一瞧 have a sleep 睡一会儿觉 have的这类短语还有很多，只要大家留意，会在以前学习过的课文中发现很多。这种短语还有自己的宾语或其它成分。例如： What a nice photo! Let me have a look (at it). You'd better have a talk with him. have还可以和表示疾病的名词连用，表示正在或曾经生过某种疾病。例如： have a headache 头痛 have a stomachache 胃痛；肚子痛