動詞不定式，為非謂語動詞。在英語語法中，動詞不定式是指動詞中的一種不帶詞形變化從而不指示人稱、數量、時態的一種形式。它之所以被稱做不定式，是因為動詞不被限定，或者說不被詞形變化所局限。不定式屬於非謂語動詞形式。
然而在一些語言裡（例如葡萄牙語），存在受時態、人稱和數量影響的不定式形態。亦有些語言完全沒有不定式，例如阿拉伯語、保加利亞語和現代希臘語。
在英語學習的課程中，動詞不定式的一般現在時被稱作“詞典用詞”，因為它一般被用作詞典中該動詞的詞頭。
動詞不定式可以作以上各種成分，但它畢竟是動詞，所以有動詞的屬性。
動詞不定式及其短語還可以有自己的賓語、狀語，雖然動詞不定式在語法上沒有表面上的直接主語，但它表達的意義是動作，這一動作一定由使動者(動詞的使用者)發出。這一使動者(動詞的使用者)我們稱之為邏輯主語。
基本介紹
- 中文名：動詞不定式
- 外文名：infinitive
- 屬性：非謂語動詞
- 表達的意義：動作
英語動詞不定式,定義,形式,疑問詞,作主語,作賓語,作補語,Find 特殊用法,作表語,作狀語,作定語,相關省略,否定式,特殊句型,相互區別,區別聯繫,語義不同,進行式,被動式,完成式,完成進行式,句型用法,"To"-不定式,不定式的時態,其它形式,德語動詞不定式,荷蘭語動詞不定式,北日耳曼語（斯堪的納維亞語支）動詞不定式,拉丁語族和羅曼語族的動詞不定式,西班牙語動詞不定式,法語動詞不定式,
英語動詞不定式
對於英語來說接不定式的單詞多為“打算”“計畫”“希望”“將要做某事”等表示未來（未做的事）的動詞。同樣與不定式表示不同,現在分詞表示正在進行，一般性或經常性發生的行為。
定義
（語態）動詞和參與此動作的主語之間關係的一個術語。當主語是動作的發起者（或之一）時，稱為主動語態；
如果動詞不定式的邏輯主語是這個不定式所表示的動作的承受者，不定式一般要用被動語態形式。如：
It's a great honour to be invited to Mary's birthday party.（不定式作主語是被動語態to be invited是被邀請）
It was impossible for lost time to be made up.（不定式作主語）
I wish to be sent to work in the country.（不定式作賓語）
Can you tell me which is the car to be repaired?（不定式作定語）
My work is to clean the room every day.（不定式作表語）
在There be結構中，修飾主語的不定式可用被動，也可用主動。如：There are still many things to take care of (to be taken care of).但有時兩種形式表達的意思不同，如：There is nothing to do now.( We have nothing to do now.) There is nothing to be done now.(We can do nothing now.)
形式
He seems to know this.
I hope to see you again. = I hope that I'll see you again. 我希望再見到你。
2) 完成式：表示的動作發生在謂語動詞表示的動作之前。
I'm sorry to have given you so much trouble.
He seems to have caught a cold.
3)進行式：表示動作正在進行，與謂語動詞表示的動作同時發生。
He seems to be eating something.
4)完成進行式：
She is known to have been wreaking on the problem for many years.
一般在表示情緒的動詞後加to do也表將來
疑問詞
①When to leave for London has not been decided yet. （不定式在句子中做主語）
②Mr. Smith didn't know whether to leave or stay there. （不定式在句子中做賓語）
③I asked Professor Xu how to learn English well. （不定式在句子中做直接賓語）
④The question was where to get the medicine needed. （不定式在句子中表語）
could learn……
經常在這種結構中使用的動詞有：consider,decide,discover,explain,find out,forget,hear,know,lea rn,observe,understand,wonder等。
作主語
動詞不定式作主語時，句子的謂語動詞常用單數，其位置有以下兩種：
(1)把不定式置於句首。如：
To get there by bike will take us half an hour.騎腳踏車到那兒將花費我們半個小時。
To make up for lost time is not possible.要彌補失去的時光是不可能的。
To lean out of the window is dangerous.身子探出窗外很危險。
To save money now seems impossible.現在好像不可能存錢。
(2)用it作形式主語，把真正的主語不定式置於句後，常用於下列句式中。如：
①It+is+名詞+to do
It's our duty to take good care of the old.照顧老人是我們的責任。
It is an offence to drop litter in the street.在馬路上亂丟廢物是違章的。
②It takes sb+some time+to do
How long did it take you to finish the work?你花了多少時間來完成這項工作？
③It+be+形容詞+for sb+to do
It is difficult for us to finish writing the composition in a quarter of an hour.我們難以在四分之一小時內完成這篇作文。
It is stupid of you to write down everything (that) the teacher says.你把老師說的所有東西都記下來的行為是很愚蠢的。
④It seems(appears)+形容詞+to do
It seemed impossible to save money.
在句型③中，常用表示客觀情況的形容詞，如：difficult,easy,hard,important,impossible,necessary 等；在句型④中，常用careless,clever,good,foolish,honest,kind,lazy,nice,right,silly,stupid,wise等 表示讚揚或批評的詞。在不定式前的sb，可看作其邏輯主語。這一句式有時相當於Sb is+形容詞+to do句式 ，如：It's kind of you to help me with my English.=You are kind to help me with my English.
⑤It + 不定式結構可位於believe/consider/discover/expect/find/think和wonder之後
He thought it would be safer to go by train.他認為乘火車比較安全。
He will find it is hard to make friends.他會感覺到交朋友困難。
⑥不定式的完成式也可作句子的主語
To have made the same mistake twice was unforgivable.兩次犯同樣的錯誤是不可原諒的。
It is better to have loved and lost than never to have loved at all.愛過而後失去了愛，比從未愛過要好。
(3)舉例
（1） It's easy (for me) to do that.我做這事太容易了
easy, difficult, hard, important, possible, impossible, comfortable, necessary, better;
the first, the next, the last, the best, too much, too little, not enough
It's so nice to hear your voice.聽到你的聲音真高興。
It's necessary for you to lock the car when you do not use it.當你不用車的時候，鎖車是有必要的。
（2） It's very kind of him to help us. 他幫助我們，他真好。
Kind, nice, stupid, rude, clever, foolish, thoughtful, thoughtless, brave, considerate(考慮周到的), silly, selfish(自私的)
例句:
It was silly of us to believe him. 我們真愚蠢，竟然相信了他。
It seemed selfish of him not to give them anything. 他不給他們任何東西，這顯得太自私了。
注意：（1） 其他系動詞如，look，appear等也可用於此句型
（3） 當不定式作主語的句子中又有一個不定式作表語時，不能用It is… to…的句型
(對)To see is to believe. 眼見為實。
(錯)It is to believe to see.
作賓語
1) 以下動詞後，只能跟不定式作賓語
afford （付得起），agree（同意），aim(力求做到)，appear（顯得），arrange（安排），ask（要求），attempt （試圖），care（想要），choose（決定），claim（聲稱），condescend（屈尊），consent（準許），decide（決定），demand（要求），determine（決心），endeavor（竭力），expect（期待），fail（未履行），help（幫助），hesitate（猶豫），hope（希望），learn（學會），manage（設法），neglect（疏忽），offer（主動提出），plan（計畫），prepare（準備），pretend（假裝），proceed（接著做），promise（答應），prove（證明），refuse（拒絕），resolve（解決），seem（覺得好像），swear（發誓），tend（往往會），threaten（預示），undertake（承諾），volunteer（自願做），vow（發誓），want（想要），wish（希望）
舉例：
The driver failed to see the other car in time.
司機沒能及時看見另一輛車。
I happen to know the answer to your question.
我碰巧知道你那道問題的答案。
decide,know,consider forget,learn,remember,show,understand,see,wonder,hear,find out,explain,tell
Please show us how to do that. 請演示給我們如何去做。
There are so many kinds of tape-recorders on sale that I can't make up my mind which to buy.有這么多的錄音機，我都拿不定主意買哪一種。
The question is how to put it into practice.
問題是怎樣把它付諸實施。
We think it quite important for us to learn a foreign language well.
He feels it his duty to help the poor.
I find it difficult to learn English well.
作補語
1) 動詞+賓語+不定式(to do)
常見動詞：advise，allow，believe，cause，challenge，compel，declare，encourage，forbid，force， find，hire，induce，instruct，invite，like，order，permit，persuade，remind，request，require，select，send，suppose，tell，train，urge
例句：
a. Father will not allow us to play on the street.
父親不讓我們在街上玩耍。
b. We believe him to be guilty.
我們相信他是有罪的。
2) to + be 的不定式結構，作補語的動詞。
常見動詞：Acknowledge, believe, consider, think, declare(聲稱), discover, fancy(構想), feel, find, guess, judge, imagine, know, prove, see(理解), show, suppose, take(以為), understand
We consider Tom to be one of the best students in our class.
我們認為湯姆是班上最好的學生之一。
3) to be +形容詞
常見動詞：Seem, appear, be said, be supposed, be believed, be thought, be known, be reported, hope, wish, desire, want, plan, expect, mean…
The book is believed to be uninteresting.
人們認為這本書沒什麼意思。
4) there be+不定式
常見動詞：believe,expect,intend,like,love,mean,prefer,want,wish,undrstand
We didn't expect there to be so many people there.我們沒料到會有那么多人在哪裡。
有些動詞需用as 短語做補語，如regard,think believe,take,consider.
We regard Tom as our best teacher. 我們認為湯姆是我們最好的老師。
Mary took him as her father . 瑪麗把他當作自己的父親。
5)禿頭不定式作補語
用禿頭不定式作賓語補足語的常用動詞如下：
口訣：“五看、三使役“，“兩聽、一感”要記住，若是“賓補”變“主補”，主補“to”字不能無。動詞let屬例外，其賓補/主補“to”均無。說明：
五看-----see/watch/notice/observe/look at；三使役-----have/make/let；兩聽-----hear/listen to；一感-----feel。
例句：I often see him go to school on foot.(禿頭不定式作賓語補足語) He is often seen to go to school on foot.(不定式作主語補足語，要帶“to”) Let him try again.---- He is let try again.(let的主補與賓補均用禿頭不定式)
Find 特殊用法
I found him lying on the ground.
I found it important to learn.
I found that to learn English is important.
作表語
不定式作表語表示具體動作或將來動作；動名詞作表語表示抽象的一般行為。
①To be kind to the enemy is to be cruel to the people.
②My chief purpose is to point out the difficulties of the matter.
③What I would suggest is to put off the meeting.
當主語和表語都是不定式時，其含義一是條件，一是結果（例①）。當主語是aim,duty,hope,idea,mista ke,plan,purpose,suggestion等為中心詞的名詞詞組（例②）時，或以what引導的名詞性分句（例③），不定 式說明主語的內容。
④Our work is serving the people.
⑤What he likes is taking a walk after supper.
⑥The story told by Mr.Wang is interesting.
④⑤句動名詞作表語，與主語部分可以轉換，如Serving thepeople is our work,而⑥句中是現在分詞作表語，說明主語的性質、狀態，現在分詞具有形容詞的各種特徵，另外，動名詞作表語還應與進行時態區別開來。
作狀語
（1）目的狀語
To… only to (僅僅為了), in order to, so as to, so(such)… as to… (如此……以便……)
He ran so fast as to catch the first bus. 他飛快地跑以便趕上第一班車。
I come here only to say good-bye to you. 我來僅僅是向你告別。
（2）作結果狀語，表事先沒有預料到的，要放在句子後面。
What have I said to make you angry.
He searched the room only to find nothing.
（3) 表原因
I'm glad to see you.
典型例題
The chair looks rather hard,but in fact it is very comfortable to ___.
A. sit B. sit on C. be seat D. be sat on
答案：B. 如果不定式為不及物動詞，其後應有必要的介詞。
當動詞與介詞連用時，常位於“形容詞+動詞不定式”結構的末尾。
作定語
⒈不定式作定語
不定式在句中作定語，置於被修飾的名詞或代詞之後。如：
①The next train to arrive is from Washington.
②Do you have anything to be taken to your sister?
③Do you have anything to say on the question?
④Would you please give me some paper to write on?
⑤My wish to visit France has come true at last.
不定式短語作定語和被修飾詞之間表示以下關係：
(1)表示將來的動作（例①）。
(4)不定式作定語時，一般可轉換為定語從句，例①to arrive=that will arrive。
相關省略
They ought to come tomorrow.他們明天應當來)：
（2）使役動詞let,have,make：
（3）感官動詞see,watch,look at,notice,observe,hear,listen to,smell,feel,find 等後作賓補，省略to。
注意：在被動語態中則to 不能省掉。
在使役動詞中get除外(get sb. to do sth.)
I saw him dance.
=He was seen to dance.
The boss made them work the whole night.
=They were made to work the whole night.
（4） 表示個人意願或傾向的would rather，had better，might(just) as well：rather than置於句首時。
Rather than ride on a crowded bus,he always prefers to ride a bike.
（5） Why… / why not…：
（6） help 可帶to，也可不帶to,help sb (to) do sth：
（7） but和except：but前是動詞do時，後面出現的動詞用不帶to的動詞不定式。
（8） 由and,or和than連線的兩個不定式，第二個to 可以省去：
（9） 通常在discover,imagine,suppose,think,understand等詞後，可以省去to be：
He is supposed (to be) nice. 他應該是個好人。
（10）but作介詞，後接不定式結構時，前面謂語動詞部分若含有do的形式時，but後的不定式要省去to，否則要帶to。
He wants to do nothing but go out.
He wants to believe anything but to take the medicine.
（11）當兩個或多個不定時短語由連詞and，but或or連線時，後一個或幾個不定式符號to常省略。但若表示對比、對照關係時，則不能省略。
He wants to move to France and marry the girl.
The purpose of new technologies is to make life easier,not to make it more difficult.
（12）不定式做表語時，一般要帶to，但若主語部分中含有do的各種形式時，符號to可省去。
We've missed the last bus.All we could do now is walk home.
否定式
Tell him not to shut the window…
She pretended not to see me when I passed by. 我走過的時候，她假裝沒看見。
特殊句型
so as to
（1） 表示目的；它的否定式是so as not to do。
Tom kept quiet about the accident so as not to lose his job.湯姆對事故保持沉默是為了不丟掉他的工作。
Go in quietly so as not to wake the baby.輕點進去，別驚醒了嬰兒。
（2) so kind as to ——勞駕
Would you be so kind as to tell me the time?勞駕，現在幾點了。
2、 "Why not +動詞原形"表達向某人提出建議
"為什麼不……?" "幹嗎不……?"
例如：
Why not take a holiday？
幹嗎不去度假？
3、It's for sb.和 It's of sb.
（1）for sb. 常用於表示事物的特徵特點，表示客觀形式的形容詞，如easy,hard,difficult, interesting,impossible等：
It's very hard for him to study two languages. 對他來說學兩門外語是很難的。
（2）of sb的句型一般用表示人物的性格，品德，表示主觀感情或態度的形容詞，如good,kind,nice,clever,foolish,right。
It's very nice of you to help me. 你來幫助我，你真是太好了。
for 與of 的辨別方法：
You are nice. (通順，所以套用of)。
He is hard. (人是困難的，不通，因此套用for。)
4、不定式的特殊句型too…to…
（1）too…to 太…以至於…
He is too excited to speak.他太激動了，說不出話來。
——Can I help you 需要我幫忙嗎
——Well,I'm afraid the box is too heavy for you to carry it,but thank you all the same. 不用了。這箱子太重，恐怕你搬不動。謝謝您。
（2) 如在too前有否定詞，則整個句子用否定詞表達肯定， too 後那個詞表達一種委婉含義，意 為“不太”。
It's never too late to mend. (諺語)
改過不嫌晚。
（3) 當too 前面有only,all,but時，意思是：“非常…” 等於very。
I'm only too pleased to be able to help you. 我非常高興能幫助你。
He was but too eager to get home. 他非常想回家。
相互區別
不定式與介詞"to"區別
to 有兩種用法：
一為不定式+動詞原形；
一為介詞+名詞動名詞，to 在下面的用法中是第二種，即to+ 名詞/動名詞：
admit to承認，confess to承認，be accustomed to 習慣於，be used to 習慣於， stick to 堅持， turn to開始，著手於， devote oneself to 獻身於， be devoted to 致力於， look forward to 盼望，pay attention to 注意
介詞but,except,besides+to do(do)
在這種句型中，如介詞前有動詞do，後面應接不帶to的不定式；如無do，則接to不定式，即帶do不帶to， 帶to不帶do。如：
The enemy soldiers had no choice but to give in.
On Sunday afternoon I had nothing to do but watch TV.
區別聯繫
1 動名詞與不定式的區別
動名詞表達的是：狀態，性質，心境，抽象，經常性，已發生的；不定式表達的是：目的，結果，原因，具體，一次性，將發生的。
2 接不定式或動名詞，意義相同
3在下列情況下，一般要用不定式：
①hate,like,love前有would(should)時，如：I'd like to have a cup of coffee.
②當謂語動詞begin,continue,start等是進行式時，如：The students are starting to work on the difficult maths problem.
③begin,continue,start與know,understand等狀態動詞連用時，如：I soon began to understand what was happening.
⒋advise,allow,encourage,forbid,permit等動詞後接動名詞作賓語，或帶不定式作賓語補足語。如：
Our teachers don't permit our/us swimming in the lake.
Our teachers don't permit us to swim in the lake.
4 部分動詞後接不定式或動名詞時，意義差別較大，應根據句子語境選擇使用。
①forget,remember,regret後接不定式，表示現在或未來的動作，接動名詞表示動作已經發生。如：
Don't forget to post the letter for me.
Have you forgotten meeting her in Beijing Airport?
Remember to close the windows before you leave.
I remember writing him a letter a year ago.
We regret to tell you that all of you are not invited to attend the meeting.
They regretted ordering these books from abroad.
語義不同
目錄
1 stop to do（停現在做的去做另一件事） stop doing（停止正在做某事）
2 forget to do（忘記去做某事） forget doing（忘記做了某事）
3 remember to do（記得要去做某事） remember doing（記得做過某事）
4 regret to do（遺憾做某事） regret doing（遺憾做了某事）
5 cease to do cease doing
6 try to do（努力做某事） try doing（試著做某事）
7 go on to do（繼續去做某事） go on doing（繼續做某事）
8 afraid to do（擔心做某事） afraid doing（擔心正在做的事）
9 interested to do（對做某事感興趣） interested doing（對正在做的感興趣）
10 mean to do（打算做某事） mean doing（做某事很有意義）
11 begin/ start to do（開始去做某事） begin/ start doing（開始做某事）
forget doing/to do
forget to do 忘記要去做某事。 (未做)
forget doing 忘記做過某事。 (已做)
The light in the office is stil on. He forgot to turn it off.辦公室的燈還在亮著，他忘記關了。(沒有做關燈的動作)
He forgot turning the light off.他忘記他已經關了燈了。 ( 已做過關燈的動作)
Don't forget to come tomorrow.別忘了明天來。 (to come動作未做)
remember doing/to do
remember to do 記得去做某事 (未做)
remember doing 記得做過某事 (已做)
Remember to go to the post office after school.記著放學後去趟郵局。
Don't you remember seeing the man before?你不記得以前見過那個人嗎？
regret doing/to do
regret to do 對要做的事遺憾。 (未做)
regret doing 對做過的事遺憾、後悔。 (已做)
I regret to have to do this,but I have no choice.我很遺憾必須這樣去做，我實在沒有辦法。
I don't regret telling her what I thought.我不為告訴她我的想法而後悔。
cease doing/to do
cease to do 長時間，甚至永遠停做某事。
cease doing 短時停止做某事，以後還會接著做。
That department has ceased to exist forever.那個部門已不復存在。
The girls ceased chatting for a moment when their teacher passed by.姑娘們在老師走過時，停了會聊天。
try doing/to do
try to do 努力，企圖做某事。
try doing 試驗，試著做某事。
You must try to be more careful.你可要多加小心。
I tried gardening but didn't succeed.我試著種果木花卉，但未成功。
go on doing/to do
go on to do 做了一件事後，接著做另一件事。
go on doing 繼續做原來做的事。
After he had finished his maths，he went on to do his physics.做完數學後，他接著去做物理。
Go on doing the other exercise after you have finished this one.作完這個練習後，接著做其他的練習
be afraid doing/to do
be afraid to do 不敢，膽怯去做某事，是主觀上的原因不去做，意為“怕”；
be afraid of doing 擔心出現doing的狀況、結果。doing 是客觀上造成的，意為“生怕，恐怕”。
She was afraid to step further in grass because she was afraid of being bitten by a snake.
她生怕被蛇咬著，而不敢在草叢中再走一步。
She was afraid to wake her husband.她不敢去叫醒她丈夫。
She was afraid of waking her husband.她生怕吵醒她丈夫。
be interested doing/to do
interested to do 對做某事感興趣，想了解某事。
interested in doing 對某種想法感興趣，doing 通常為想法。
I shall be interested to know what happens.我很想知道發生了什麼事。(想了解)
I'm interested in working in Switzerland. Do you have any idea about that
我對在瑞士工作感興趣。你想過這事嗎? (一種想法)
mean doing/to do
mean to do 打算、想
mean doing 意味著
I mean to go,but my father would not allow me to.我想去，但是我父親不肯讓我去。
To raise wage means increasing purchasing power.增加工資意味著增加購買力。
begin(start) doing/to do
begin / start to do sth
begin / start doing sth.
（1) 談及一項長期活動或開始一種習慣時，使用doing.
How old were you when you first started playing the piano你幾歲時開始彈鋼琴？
（2) begin,start用進行時時，後面動詞用不定式to do
I was beginning to get angry。我開始生起氣來。
（3) 在attempt,intend,begin,start 後接know,understand,realize這類動詞時，常用不定式to
do。
I begin to understand the truth。
我開始明白真相。
（4) 物作主語時
It began to melt.
⒉動詞不定式的時態，語態
(1)時態
①一般式：動詞不定式一般式表示的動作發生在謂語動詞之後，有時表示同時發生.如：
I hope to become a university student this year.(to become發生在hope之後)
We often hear Dick play the piano in the next room.(play和hear同時發生)
②完成式：表示的動作發生在謂語動詞所表示的動作之前.如：
I'm sorry to have kept you waiting.
We are too young to have seen the old society.
③進行式：表示的動作與謂語動詞同時發生.如：
The teacher happened to be correcting our papers when I came in.
They seemed to be discussing something important.
(2)語態
如果動詞不定式的邏輯主語是這個不定式所表示的動作的承受者，不定式一般要用被動語態形式，如：
It's a great honour to be invited to Mary's birthday party.(不定式作主語)
It was impossible for lost time to be made up.(不定式作主語)
I wish to be sent to work in the country.(不定式作賓語)
Can you tell me which is the car to be repaired (不定式作定語)
He went to the hospital to be examined.(不定式作狀語)
在There be結構中，修飾主語的不定式可用被動，也可用主動，如：There are still many things to take care of (to be taken care of).但有時兩種形式表達的意思不同，如：These is nothing to do now.( We have nothing to do now.) There is nothing to be done now.(We can do nothing now.)
⒊動名詞的時態，語態
(1)時態
①一般式：動名詞的一般式所表示的動作可以是泛指，也可與謂語動詞同時發生，或發生在謂語動作之前或之後，如：
We are interested in collecting stamps.
I shall never forget seeing the Great Wall for the first time.
We are not afraid of dying.
②完成式所表示的動作發生在謂語動詞之前，如：
Imagine having travelled on the moon.
We were praised for having finished the work ahead of time.
(2)被動語態
①如果動名詞的邏輯主語為動名詞所表示的動作的承受者，動名詞要用被動語態，動名詞的被動語態有一般式與完成式之分，如：
The young man came in without being noticed.
He prided himself on having never been beaten in class.
②有些動詞後的動名詞用主動形式，但表示被動意義，如：
The bike needs repairing.
If a thing is worth doing,it is worth doing well.
⒋在口語中，為避免重複，常用“to”代替不定式結構，有時甚至可以把to省略，如：
①-Did you go to visit the Great Wall
-No,I wanted to,but there wasn't enough time.
②-Would you like to come to a party
-I'd love to.
③-Don't make any mistakes in your homework,will you
-I'll try not to.
④-Try to be back by 12,won't you
-OK,I'll try.
另外，be going to,ought to,used to等也常用於這一結構中。
⒌在why引起的問句中，省略“to”，如：
Why spend such a lot of money
Why not wait for a couple of days
⒍當兩個或更多作用相同的不定式並列使用時，只在第一個不定式前加“to”，如：
It's quite necessary for us to read more and have more practice.
devote…to,face up to(勇敢地面對),look forward to(盼望),object to(反對),take to(養成習慣，對……感興趣；開始從事某種活動),be used to(習慣於)等。
進行式
形式
to be + 現在分詞
He seems to be following us.他好像在跟著我們。
用法
①用於助動詞之後
He must be coming by bus.他一定是乘公共汽車來的。
You shouldn't be reading a novel.現在你不應該看小說，你應該看課本。
②用於appear，happen，pretend，seem之後
I happened to be standing next to him when he collapsed.相當於：
It happened that I was standing next to him when he collapsed.他倒下的時候我恰巧站在他身邊。
③hope 和promise之後，或agree，arrange，decide，determine/be determined，plan，undertake之後，但用於hope和promise後更常見：
I hope/hoped to be earning my living in a year's time.相當於：
I hope I will/I hoped I would be earning……我希望在一年之內能自食其力。
被動式
不定式被動式的用法
不定式到底用主動形式還是被動形式，往往取決於句子的意思，即意思上為主動就用主動形式，意思上為被動就用被動形式：
Did it need to be done so soon? 這事需要這么快就做嗎?
She can’t bear to be laughed at. 她受不了被人嘲笑。
There was business to be taken care of. 有生意要人管理。
It remains to be seen whether you are right. 你是否正確，以後見分曉。
There was a lot of rubbish to be got rid of. 有大量垃圾需要扔掉。
不定式完成被動式的用法
不定式的完成被動式表示發生在謂語動作之前的被動動作：
I’m pleased to have been given this opportunity. 給了我這次機會我很高興。
It’s said to have been built in the Ming dynasty. 據說它是明朝修建的。
完成式
表示發生在謂語動作之前的動作
He seems to have caught a cold. 他似乎感冒了。
I hate to have quarreled with her. 我後悔和她吵架了。
I believe it to have been a mistake. 我相信這是一個錯誤。
You appear to have travelled quite a lot. 你似乎作過多次旅行。
I’m sorry to have given you so much trouble. 對不起給了你這么多麻煩。
It’s said to have been built in the Ming dynasty. 據說它是明朝修建的。
表示在某個給定的時間之前已完成的動作
I hope to have finished the work by now. 我希望現在以前已完成這項工作。
表示過去未曾實現的想法和願望
I should like to have come earlier. 我本想早點來的。
We were to have been married last year. 我們本來打算去年結婚的。
完成進行式
形式
to have been + 現在分詞
He seems to have been spying for both sides.
他似乎一直在為兩方面搞秘密情報。
用法
只要用於助動詞之後和appear，seem之後，但也可以用在happen，pretend以及believe，know，report，say，understand的被動式之後：
He appears to have been waiting a long time.相當於：
It appears that he has been waiting a long time.
看來他已經等了很久了。
He pretended to have been studying. 相當於：
He pretended that he had been studying.
他假裝一直在學習的樣子。
句型用法
For example one,There are too much homework to write.
two,There are students writing too much homework.
"To"-不定式
在英語中不定式最常用於質詞"to"之後， 例如在 "to walk", "to cry", "to eat", "to fear".這種用法叫做to-infinitive。莎士比亞在著作哈姆雷特的獨白時就大量採用了這類不定式動詞。
- To be or not to be ...
- To sleep, perchance to dream ...
經常跟在to後形成不定式的動詞包括:
例如:
- I arranged to stay the night. ("我已安定好今晚留在這裡。")
- We intend to go skiing this weekend. ("我們打算這個周末去滑雪。")
- I swear to honour you. ("我發誓為你增光。")
- He sought to notify them of this new occurrence.
這些有賓詞，然後加上有to的不定式的動詞包括 (連同以上帶有星號的動詞): advise, allow, challenge, command, compel, condemn, enable, encourage, expect, forbid, force, help, induce, inspire, instruct, invite, oblige, order, permit, persuade, prefer, program, remind, teach, tell, train, urge, warn.
有些動詞之後加 for + 賓詞 + to-然後不定式. 通常這些動詞包含渴望的意思，不能單單在後面加上賓詞和不定式 (though an infinitive alone may work). 這些動詞包括 apply, arrange, ask, call, clamour, long, opt, plead, press, vote, wait, wish, yearn.
例如:
- I have arranged for the neighbour to water the plants. （“我已安排好鄰居給植物給水。”）
- I pleaded for him to accompany me to the theatre. （“我懇求他陪我去看戲。”）
不定式的時態
Infinitives in English exist in many aspects. Here is a table showing these different tenses for the verb to cook.
一般時 | (to) cook | (to) be cooked |
進行時 | (to) be cooking | / |
完成時 | (to) have cooked | (to) have been cooked |
完成進行式 | (to) have been cooking | / |
其它形式
德語動詞不定式
在德語中，動詞不定式常以-en結尾，如sagen，-en前的部分為動詞詞幹(sag-),但也有少部分以-ern、-n或eln結尾。動詞前的zu的用法與英語類似。
作名詞
作主語
部分德語不定式可用作主語，如anfangen, aufhören, beginnen, andenken, glauben, hoffen, meinen, vergessen, versuchen.
例句：Sie meint, sie hat immer recht -> Sie meint, immer recht zu haben- 他認為他總是對的。
荷蘭語動詞不定式
在荷蘭語中，不定式也以-en結尾。在動詞前使用te，用法與英語to相似。
如Het is niet moeilijk te begrijpen. -這不難理解。
北日耳曼語（斯堪的納維亞語支）動詞不定式
北日耳曼語通常沒有類似英語to的詞。
