3.可省可不省的： help sb. （to）do sth . 精品 PPT I often help my mother （to）do housework.
?否定形式：
（1）动词不定式的否定式是直接在to之前加not. 例：Tell them not to play football in the street.
一. 作主语：
? To be a doctor is hard. ? To learn English well is not easy.
? 动词不定式短语作主语时，为了避免句子的头重脚 轻，可以用“ it”作形式主语，而把真正的主语－动词不 定式短语放在句子的后部。 例如上面的句子可以表示为：
It is hard to be a doctor. It is not easy to learn English well. 再如： It's important to plant trees in spring.
精品 PPT
He hopes to become a teacher.
三. 作宾语 动词不定式（短语）可以放在一些动词后面用作宾语，
能以动词不定式作宾语的动词有： begin, want, remember, agree, learn, like, decide, fail, pretend, demand,refuse 等。例：
精品 PPT
1.不可以省to的不定式作宾语补足语： tell /ask / want / would like / wish / suppose / invite /encourage
/teach/ depend on等 + sb.+ to do sth. 例：
? The teacher told us to come earlier tomorrow. ? I want you to go now. ? Her parents wish her to be a teacher.
注意： （1）如果and 连接两个动词不定式，第二个动词 不定式一般省“ to”例：
He wants to go and have a swim with us. （2）若作宾语的动词不定式（短语）很长，可用 it
作形式宾语。 I find it interesting to learn English with you.
（2）省to的动词不定式的否定式是直接在动词前面加not. 例： Let the boy not go.
动词不定式用法小结
精品 PPT
? 动词不定式是一种非谓语动词形式，其结构为“to＋
动词原形”，其中to不是介词，而是动词不定式的符 号，称为小品词，动词不定式没有人称和数的变化。 动词不定式和其后面的名词等构成不定式短语，在句 子中可以用作主语、表语、宾语、补足语、定语、状 语等。
精品 PPT
To look after my pets properly takes a lot of time.
? 如果表示动词不定式的动作执行者，可以在不定式前 面加一个由介词 for引导的短语，称为不定式的复合结构。 例：
? It's good for us to read English aloud in the morning. 精品 PPT
? It is important for students to use English every day.
精品 PPT
He found it hard to catch up with others.
பைடு நூலகம்
The teacher advised him to try another way.
四. 作宾语补足语。 例如：
?The teacher asked us to read English for half an hour in the
2.省“to”的不定式作宾语补足语：
? Let / make / have + sb. +do sth. ? Let the boy go out now. ? The boy made the baby cry. ? see / watch / hear / notice / feel + sb. +do sth. ?I saw the students play basketball on the playground yesterday. ? I often hear the girl sing in the next room.
morning.
? The teacher often tells Jim not to spend too much time
playing computer games.
? Please let me help you. ? 动词不定式作宾语补足语，表示宾语所做的动作，可
以用动词不定式作宾语补足语的动词有： tell, ask, want, like, invite, encourage, help 等。但在let, make, see, watch, hear, feel, notice, have 等感官听觉动词或使役动词 后面作 宾语补足语的动词不定式一般要省略动词不定式符号 “to”，可以归纳为以下三种句式：
My ambition is to work for firm that develops computer software when I grow up.
二. 作表语： 动词不定式（短语）作表语常用于系词be的后面。例：
His work is to drive a car. My job is to feed animals. Her ambition is to be a doctor.
? I want to tell you a story. ? They begin to work at eight every morning. ? Don't forget to lock the door. ? Would you like to go and have a picnic with us tomorrow?