不定式可以有多种形式，如：主动式（to drink, to see）、被动式（to be continued, to be understood）、完成式（to have completed, to have been adopted）、进行式（to be leaving）等

　　不定式在句中常作下列成分：

　　考点一 不定式作宾语、主语或表语

　　1. 作宾语：不定式多接在谓语动词后作宾语

　　如：He decided to put in a good word for me at the meeting.

　　I didn't expect to hear from you so soon.

　　常用的可接不定式宾语的动词有：decide, expect, determine, offer, forget, remember, want, prefer, wish, hope, continue, begin, attempt, agree, etc.

　　例：Human beings are social animals who usually prefer not to live in physical or psychological isolation.

　　2. 作主语：不定式短语可作主语

　　如：To see is to believe (百闻不如一见)

　　To work hard should be your major concern.

　　注意：由于英文不习惯句子主语过长，不定式主语常被形式主语it所代替(详见第十七章)

　　例如上面第二句可以变为： It should be your major concern to work hard.

　　又如： It is very nice of you to help me.

　　It is hard for you to carry this heavy box.

　　3. 作表语：当句子的主语是purpose, aim, duty, goal, hope, plan, suggestion, idea, intention, problem, mistake, reaction等表示“意图”、“目的”、“功能”等意思的词时，一般由不定式作表语

　　如：His only purpose in life is to seek truth.

　　Our plan was to raise money for the new project.

　　例题：

　　Chinese immigrants began ---- to the United States in large numbers in the middle of the nineteenth century.

　　(A) come

　　(B) to come

　　(C) to have come

　　(D) have come

　　答案：B

　　解释：空格处需要began的宾语，可以是动名词或不定式，A, D是动词原形，可先排除；C是不定式的完成式，不符合begin的用法；只有B正确

　　考点二 不定式作定语

　　不定式常接在名词之后作定语，如：

　　something to read,                  nothing to do,        anything to declare,

　　a lot to complain of,          the right person to talk to, etc.

　　由上述例子不难看出不定式和被修饰词间有动宾关系，因此不及物动词之后必须加上相搭配的介词（例如上面的complain + of, talk +to）

　　不定式定语还可表示将来的含义，如：in the years to follow, the meeting to be held in June

　　针对TOEFL解题需注意下列情况：

　　1. 由序数词修饰的名词之后多用不定式作定语，

　　如：the first one to arrive, the last to mention, the only thing to talk about

　　例句：Not only was the Mariner spacecraft the first to fly beyond Mars, but it also survived in space well past its expected lifetime of twenty-one months.

　　2. 改错题常出现名词之后直接接动词，且二者间不是主谓关系而是动宾关系，此处必定有错，应在动词前加to，变为不定式作定语

　　如：Do you have anything declare (错)

　　Do you have anything to declare (对) （你有什么东西需要申报的吗？)

　　3. 少量题中出现了类似定语从句的不定式作定语，其基本形式为：介词+关系代词+不定式，如：Here is a blue pen, with which to fill out the form.

　　例题

　　(1)

　　An innovator, ballerina Augusta Maywood was ---- a traveling company.

　　(A) to form the first

　　(B) the first to form

　　(C) who formed the first

　　(D) forming the first

　　答案：B

　　解释：空格前是句子的主谓语, 空格处需要was的表语, first不能和a连用, 故A、C、D肯定不对; B中the first作表语, 省略了后面的person, 不定式to form…作定语, the first to do是常见用法, 表示第一个做某事的人

　　考点三 不定式作状语

　　不定式作状语是相当普遍的语法现象，通常表示目的、结果或原因

　　如：I got an early morning to catch the first train to London. (表目的)

　　She raised the lid only to find an empty bottle. (表结果)

　　He trembled to think of his shameful failure. (表原因)

　　TOEFL种主要涉及第一种用法

　　考点四 是否用不定式

　　1．有部分动词的习惯用法要求采用不定式复合结构，其基本形式为：动词+宾语+不定式，

　　如：enable him to dance,          cause the little girl to cry,

　　consider it to be a great honor,          imagine herself to a soprano

　　常接不定式复合结构的词有：allow, enable, cause, ask, expect, invite, advise, permit, oblige, help, encourage, persuade, instruct, command, urge, consider, believe, declare, etc.

　　注意：help既可以接不定式，也可以接动词原形（或称不带to的不定式），

　　如：help him to clean the lab,  help me do the housework

　　例题：

　　(1)

　　The flexibility of film allows the artist ----unbridled imagination to the animation of cartoon characters.

　　(A) to bring

　　(B) bringing

　　(C) is brought

　　(D) brings

　　答案：A

　　解释：allow somebody to do sth.属于固定动词词组搭配,

　　若allow之后无宾语则用allow doing 的形式。

　　2. 在一些表示“意图”、“目的”、“倾向”等意思的动词、形容词后面经常要跟不定式，而表示同样意思的名词后面经常需要用不定式做定语

　　例句：

　　Having lost the election, the presidential candidate intend to support the opposition despite the objections of his staff.

　　Many modern photographers attempt to manipulate elements of photography other than light in their photographs.

　　这样的动词还有tend,  plan,  expect,  endeavor,  try,  wish等

　　He is anxious to go home.

　　I am inclinded to work in Shanghai.

　　这样的形容词还有able, apt, eager, glad, ready, likely等

　　A loan may be acknowledged by a bond , a promissory note, or a mere promise to repay.

　　He has the inclination to grow fat.

　　这样的名词还有ablility , effort , attempt, anxiety,determination, inclination, plan 等

　　例题：

　　(1)

　　Billie Holiday's reputation as a great jazz-blues singer rests on her ability ----emotional depth to her songs.

　　(A) be giving

　　(B) are given

　　(C) being given

　　(D) to give

　　答案：D

　　解释：此句主谓俱全, 主语reputation, 谓语rests on, 缺少宾语ability的修饰成分. 根据谓语唯一原则可首先排除A B； C是被动式, 后面不能有宾语, 亦可排除; D为不定式作定语, the ability to do即做某事的能力