動詞不定式的用法
一、動詞不定式在句子中不能充當謂語，沒有人稱和數(shù)的變化。
二、動詞不定式是由“to+動詞原形”構(gòu)成(有時可以不帶to)。動詞不定式的否定形式是“not+動詞不定式”(not不與助動詞連用)。
三、動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，表語的形容詞為kind，nice，good，polite，clever，foolish，right，wrong等表示評價的形容詞。
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、賓語補足語：
(1)在多數(shù)復合賓語及物動詞后要帶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、形容詞補足語：在表示心理、感情、評價等的形容詞后，對其進行補充說明。
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“不定式被動語態(tài)一般式(tobe+過去分詞)”。
例：There are twenty more trees to be planted.