(5)作定語：

　　動詞不定式作定語，放在所修飾的名詞或代詞后。與所修飾名詞有如下關系：

　　①動賓關系：

　　I have a meeting to attend.

　　注意：不定式為不及物動詞時，所修飾的名詞如果是地點、工具等，應有必要的介詞，如：

　　He found a good house to live in.

　　The child has nothing to worry about.

　　What did you open it with?

　　如果不定式修飾time, place, way，可以省略介詞：

　　He has no place to live.

　　This is the best way to work out this problem.

　　如果不定式所修飾名詞是不定式動作承受者，不定式可用主動式也可用被動式：

　　Have you got anything to send?

　　Have you got anything to be sent?

　　②說明所修飾名詞的內容：

　　We have made a plan to finish the work.

　　③被修飾名詞是不定式邏輯主語：

　　He is the first to get here.

　　(6)作狀語：

　　①表目的：

　　He worked day and night to get the money.

　　She sold her hair to buy the watch chain.

　　注意不定式放句首時，邏輯主語與句子主語要一致：

　　wrong：To save money, every means has been tried.

　　right：To save money, he has tried every means.

　　wrong：To learn English well, a dictionary is needed.

　　right：To learn English well, he needs a dictionary.

　　②表結果：

　　He arrived late to find the train gone.

　　常用only放在不定式前表示強調：

　　I visited him only to find him out.

　　③表原因：

　　They were very sad to hear the news.

　　④表程度：

　　It's too dark for us to see anything.

　　The question is simple for him to answer.

　　(7)作獨立成分：

　　To tell you the truth, I don't like the way he talked.

　　(8)不定式的省略：保留to省略do動詞。

　　If you don't want to do it, you don't need to.

　　(9)不定式的并列：第二個不定式可省略to。

　　He wished to study medicine and become a doctor.