1. 動詞know后不能直接跟不定式作賓語，只能跟疑問詞+不定式。

　　There isn’t any difference between the two. I really don’t know which to choose.

　　I don’t know whether to stay or not.

　　類似的動詞有：show, ask, tell, explain, consider, find out, understand, etc.

　　注意：不定式與only連用表示一種意外或不幸的結果。

　　I went to see him only to find him out. 我去看他，不料他出去了。

　　2. 以下短語常跟不帶to的不定式。

　　might as well would rather would sooner(寧愿)

　　would as soon had better had rather (寧愿)

　　may just as well (還是……的好) prefer … rather than

　　rather than (而不是) had sooner (寧可，寧愿)

　　He preferred to stay at home rather than go out.

　　She said she had sooner live in the city than on a farm.

　　3. 介詞but, except, save, than等后接不定式。

　　1) but后常跟帶to的不定式，只有在下列短語中but后不帶to。

　　do anything/everything/nothing but cannot help but

　　cannot but cannot choose but

　　The sailor did nothing but complain about the food.

　　Can’t you do anything but ask silly questions?

　　2) 當but連接兩個平行結構時，會出現帶to的不定式。

　　They went to America not to study English but to do business.

　　3) 在have no (any) choice/alternative but結構中，不定式帶to。

　　I think you have no choice but to go with me.

　　I had no alternative but to do as you tell me.

　　4) 介詞except, than后既可跟帶to的不定式也可跟不帶to的不定式。

　　She did nothing else than (to) laugh. 她只是哭。

　　4. 動詞help, bid, know等既可跟帶to的也可跟不帶to的不定式作賓語補足語。

　　Will you help me (to) make the plan?

　　The king bids all subjects (to) pay the tax.

　　注意：動詞know前面的時態是現在時，通常用to be作賓語補足語;若其前面為過去時或完成時，可用其它動詞作賓語補足語。

　　I know him to be a liar.

　　I have never known her (to) sing so beautifully.

　　They knew him to have come.

　　5. 當不定式作賓語，其后又跟有賓語補足語時，應用it作形式賓語，真正的賓語應置于句末。常用于這一句型的動詞有find, feel, think, consider, deem(相信，認為), make, believe等。

　　Do you consider it wise to ignore them?

　　I find it very difficult to study English well.

　　6. 以下動詞常跟不定式的完成時作賓語：

　　seem suppose mean wish hope expect

　　promise appear would happen pretend

　　I meant to have telephoned, but I forgot. 我本打算打個電話，但后來忘了。

　　She wished to have come here last night, but she had no time.

　　注意：在美國英語中intended或had intended其后的不定式采用一般式就可表示希望，打算或意圖未曾實現，不應用不定式的完成時，TOFEL考試將此評為錯誤。

　　I intended to come, but a heavy rain prevented me from coming.

　　I intended to write her a letter yesterday, but I forgot to because of the day and evening appointments that I had.

　　7. 以下短語常跟不定式的完成時作主補：

　　be believed/found/known/said/reported/supposed

　　be thought/understood…

　　He is said to have translated the book into Chinese.

　　You are supposed to have read the instructions.

　　8. deserve, need, require, want 前的主語為有生命的人或物時，后常接不定式。

　　She deserves to win because she was the best.

　　The boy needs to study hard.

　　注意：若主語為無生命的事物，其后常接不定式的被動式，動名詞的主動式。

　　These flowers need to be watered at once.(… watering at once.)

　　This point deserves mentioning. (… to be mentioned.)

　　9. 當不定式與其所修飾的名詞構成動賓關系，不定式又是不及物動詞時，后面要加相應的介詞。

　　He is a very good comrade to get along with.

　　We want to find a place to live in.

　　10. have與get后接不定式作賓補時，get后的賓補前應加to.

　　I’ll have a worker repair the door.

　　or:

　　I’ll get a worker to repair the door.

　　11. 不定式的邏輯主語

　　一般情況下不定式的邏輯主語就是句子的主語。

　　He studies hard to get high scores.

　　但有兩種特殊情況

　　1) 由for引出邏輯主語。

　　This is a very difficult for us to answer.

　　2) 如果形容詞是指行為的性質又同時指行為的人即表示人的性格、特征等，由of引出邏輯主語，常見的形容詞有：

　　kind foolish good wise stupid honest

　　brave wrong right considerate rude bold

　　nice impolite courageous wicked clever silly

　　It’s kind of you to give me so much help.

　　It’s foolish of you to behave like that.