八年级下册辅导——含有动词不定式不定式用法讲解 和句式归纳 不定式用法讲解
1. 不定式的基本形式：to + 动词原形，有时可以省略to。 2. 动词不定式的特点：
（1）没有人称和数的变化，在句子中不能作谓语。
（2）动词不定式仍保留动词的特点，可以有自己的宾语和状语。动词不定式同它的宾语或状语可构成动词不定式短语。例如：to read a book;（3）动词不定式具有名词、形容词和副词的特征，因此在句中可以作主语、表语、宾语、宾语补足语、定语和状语。
3. 动词不定式作宾语：即不定式直接跟在谓语动词后，是谓语动词涉及的直接对象，如果没有这个不定式，这个句子的意思就让人难以理解。能直接带不定式作宾语的及物动词主要有：
want, like, love, need, try, ask, learn, begin, start, forget, remember, hope, decide, afford, offer, make sure, would like, plan, hate, try one’s best等。
My mother agrees to buy a pair of sports shoes for me. We decide to have a party. She hopes to be an engineer. As the lights turned green. All the cars started to go. Sorry. I forgot to tell you about the news. Tom remembered to leave the keys on the desk.
Mr Liu is arranging to have an Speaking English competition. Mary hates to climb mountains. 4. 动词不定式作宾语补足语：能用动词不定式作宾语补足语的动词有：
ask, tell, get, order, would like, want, teach, show, allow, encourage, warn, wish, invite, help等。
She often invites us to take part in her party. Mom always tells me to go home on time. Our teachers encouraged us to work hard on our subjects. 5. 动词不定式作宾语补足语省略to的场合：
（1）作动词let, make, have, feel, hear, see, watch, notice等的宾语补足语时，动词不定式不带to。
Let him do the work. He made me work day and night. I saw him fall off the bike. （2）作动词help的宾语补足语时，动词不定式可带to, 也可不带to。
He didn’t help me (to) mend the bike. You have helped (to) protect our environment. 6. 动词不定式的否定形式：not to + 动词原形
Tell him not to be late. I will try not to read in bed.
Remember not to waste water. 7. 动词不定式作状语：即不定式直接跟在谓语动词后，仅对谓语动词起一个补充说明的作用，如果没有它，句子意思仍然完整，它不像作宾语那样，与谓语动词有着密切的关系。
（1）表示目的： I sat down to have a rest. He stopped to have a look.
He rushed into the room to save the girl. He got up early to catch the train. （2）表结果：
The girl cried to make her mother angry. （3）表示程度：
She is too tired to walk any farther. She is strong enough to carry the heavy box.
I was surprised to read the news 动词不定式（短语）在句中可以做主语，宾语，表语，定语，宾补，状语，还可以和疑问词连用，作句子的主语，宾语，表语等。与动词不定式有关的句式也很多，常见的含有动词不定式的句式主要有以下几种： 一.
It takes sb. some time （money）to do sth. 某人花费多少时间（金钱）做某事。例如：
1. It often takes me half an hour to watch TV every evening. 每天晚上我常常用半小时看电视。
2. It took me ten yuan to buy the book last week. 上周我花了10元买那本书。
3. How long will it take them to finish the work? 完成那项工作需要花费他们多少时间？
在使用该句式要注意的是：sb. 如果代词表示用宾格；take随时态改变；句中的时间用段时间，对此提问用how long。
例：It takes us more than two hours to do our homework every day. It took us more than two hours to do our homework yesterday. It will take us more than two hours to do our homework tomorrow. How long did it take you to do your homework yesterday?
二. It’s time to do sth. 该做某事了，同义句为： It’s time for sth. / doing sth. 例： It’s time to go to school. 该上学了。 （It’s time for school.） It’s time to get up. 该起床了。 （It’s time for getting up.）
此句可以扩展为：It’s time for sb. to do sth. 是某人做某事的时间了。 It’s time for me to work. 到我工作的时间了。 It’s time for you to go to school.
到你们上学的时间了。
三. 主语＋be（not）+adj.+enough to do sth. （某人、某物）足够（不能）做某事。例：
The boy is old enough to go to school. 这个孩子到了上学年龄。 I’m tall enough to reach the top of the tree. 我够高能够到树顶。 *1. 此句是肯定句时，可以用主＋be＋so＋adj.＋that的句型（即so?,that?表示的结果状语从句）来替换。 The boy is so old that he can go to school.
I’m so tall that I can reach the top of the tree.
2. 此句是否定句式时，既可以用so?that?引导的结果状语从句来替换，还可以用too?to?句式替换。例： He is not old enough to go to work. 他太小不能去上班。
He is so young that he can’t go to work. He is too young to go to work.
四. sb. +be ready + to do sth. （某人乐意做某事） He is always ready to help others. 他总是乐于帮助别人） I’m always ready to make new friends. 我总是乐于结交新朋友。 五. It’s +adj. + for / of sb. to do sth. 对某人来说做某事?例：
It’s dangerous for children to play football in the street. 对孩子来说在街上踢足球是很危险的。