Ⅰ. 不定式句法功能
1. 作主語：The cat said, “To take roller coaster” is terrible.
不定式短語作主語時(shí)，可以直接放在句首，但在很多情況下，尤其是在疑問句和感嘆句中，往往放在謂語之后，而用先行代詞it作形式主語。
→ The cat said, “It’s terrible to take roller coaster.”
How long did it take you to take roller coaster?
How terrible it is to take roller coaster?
不定式作主語常見句型：
a) It is adj. (easy, important, difficult…) 不定式
b) It is n. (a pity, a pleasure, one’s duty, a shame) 不定式
eg. It’s my duty to teach you how to be a student of No.3 Middle School.
c) It takes/needs/requires some time (hours, months, days, patience…) 不定式
eg. It requires patience to be a good teacher.
2. 作表語：當(dāng)句子的主語是aim, idea, policy, question, suggestion, wish, task, duty, job, purpose等或者主語是what引導(dǎo)的名詞性從句時(shí)，后面可以用不定式做表語，用以說明主語所包含內(nèi)容。
eg. Our most important task now is to make a plan.
注：作表語的不定式都帶to，但當(dāng)主語部分有實(shí)義動(dòng)詞do時(shí)，to可以省略。
eg. The only thing we can do now is wait and see.
3.作賓語
The cat said “Remember not to take it next time!”.
a) 可以直接用不定式作賓語的動(dòng)詞很多，常見的有：agree, afford, tend, ask, decide, determine, expect, fail, hope, learn, intend, manage, offer, plan, promise, refuse, want, wish等
2005年天津卷12題：I don’t want _____ like I’m speaking ill of anybody, but the manager’s plan is unfair.
A. to sound B. to be sounded C. sounding D. to have sounded
當(dāng)不定式短語比賓補(bǔ)長時(shí)，往往將不定式放到賓補(bǔ)后，而用先行代詞it作形式賓語，常用動(dòng)詞有feel, think, find, believe, consider, make等。
The cat felt it terrible to take roller coaster.
b) 不定式一般不作介詞的賓語，只有少數(shù)介詞如but, except等后面可以跟不定式作賓語。一般情況下作介詞賓語的不定式都帶to，如果but或except所在句子里的謂語動(dòng)詞都是實(shí)義動(dòng)詞do, does, did時(shí)，通常省略to。
 

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