動(dòng)詞不定式的用法
一、動(dòng)詞不定式在句子中不能充當(dāng)謂語，沒有人稱和數(shù)的變化。
二、動(dòng)詞不定式是由“to+動(dòng)詞原形”構(gòu)成(有時(shí)可以不帶to)。動(dòng)詞不定式的否定形式是“not+動(dòng)詞不定式”(not不與助動(dòng)詞連用)。
三、動(dòng)詞不定式短語具有名詞、形容詞和副詞等的功能，可在句中用做多種句子成分。
1、主語：常置于句末，而用it代替其做形式主語。例：
To go in for sports helps you stay fit.
It helps you stay fit to go in for sports. It is dangerous to swim in the deep sea on your own.
注：此句式中不定式邏輯上的主語可由for或of引出，邏輯主語由of引出時(shí)，表語的形容詞為kind，nice，good，polite，clever，foolish，right，wrong等表示評(píng)價(jià)的形容詞。
例：It's right of him to refuse the invitation1.(him為邏輯主語)
2、表語：Our duty is to protect the enviroment.
3、動(dòng)詞賓語：此種情況可按固定搭配或句式去記。
例：would you like to see my photos?
Kevin planned to visit his uncle.
和plan用法一樣的詞還有：start，want，agree，hope，begin，decide等。
I found it very difficult to get a job.(it為形式賓語)
4、賓語補(bǔ)足語：
(1)在多數(shù)復(fù)合賓語及物動(dòng)詞后要帶to。
例：I asked a friend to read it to me.(book4，L2)
(2)在表示感覺、致使等意義的動(dòng)詞(see，watch，hear，feel，notice，observe，make，let，have，help等)后不帶to。
例：They heard him sing a pop song in the meeting room.
5、定語：動(dòng)詞不定式做定語放在所修飾的名詞的后面。
例：Vinny is the first disabled2 person to sail3 around the world.
6、形容詞補(bǔ)足語：在表示心理、感情、評(píng)價(jià)等的形容詞后，對(duì)其進(jìn)行補(bǔ)充說明。
例：Weareverygladtomeetyouagain.
7、狀語：表示目的、原因、程度等。
例：They brought in photos of their families for me to look at.
8、“疑問詞+不定式”用法：不定式前可帶what，who，which，where，when，how等疑問詞，這種不定式短語在句中多用做賓語。
例：He didn't tell me where to go.
9、在初中階段還涉及到“不定式被動(dòng)語態(tài)一般式(tobe+過去分詞)”。
例：There are twenty more trees to be planted.