動(dòng)詞不定式通常帶有符號to，叫做帶to的動(dòng)詞不定式(infinitive with"to")，動(dòng)詞不定式有時(shí)不帶符號to，叫做不帶to的動(dòng)詞不定式(infinitive without"to")。不帶to的動(dòng)詞不定式通常有下面十八種情況
一、與助動(dòng)詞do連用構(gòu)成謂語動(dòng)詞的否定、疑問和強(qiáng)調(diào)形式。
(1)he does not work in the factory.
(2)Does she work here？
(3)I did not see her yesterday.
(4)Did they take you home?
(5)He does look tired.
(6)They did come yesterday.
二、與情態(tài)動(dòng)詞連用構(gòu)成復(fù)合謂語
(1)I can speak English.
(2)May I come in?
(3)Dare he swim across the river?
(4)We must work,and above all we must believe in ourselves.
(5)Could you do something for me?
(6)You shall go at once.
(7)He might be working in the office now.
(8)I don't think you need have come yesterday.
(9)They should be here by now.
(10)If you will go into the fields and turn over a few big stones,you are sure to uncover a city of ant"people".
但與情態(tài)動(dòng)詞ought(to)連用時(shí)通常帶to，和used(to)連用時(shí)必須帶to
三、在表示感覺的動(dòng)詞如：see,look.at,watch,hear,listen to,feel,notice,observe,perceive(覺察，看見),behold（書面用語“見到”）等后用作賓語補(bǔ)足語的動(dòng)詞不定。
(1)I saw her cross the street.
(2)He looked at the children walk up the hill.
(3)I watched the boy cross the road.
(4)I heard her play the piano.
(5)He listend to us talk.
(6)I felt the floor move.
(7)I didn’t notice you enter.
(8)He observed someone open the door.
(9)I did not perceive anyone come in.
(10)He beheld her go out.
但除notice,watch不用被動(dòng)語態(tài)外，上述動(dòng)詞變成被動(dòng)語態(tài)時(shí)，其后的動(dòng)詞不定式就不省to
(1)She was seen to cross street.
(2)She was heard to play the piano.
四、使役動(dòng)詞make,let,have,bid, leave(=let)后作賓語補(bǔ)足語的動(dòng)詞不定式不帶to
(1)You may take a horse to the water,but you can't make him drink.
(2)I'll let him do it.
(3)Don't forget to have them come.
(4)Bid him go home.
(5)Leave him go.
動(dòng)詞have通常不用于被動(dòng)語態(tài)，make和bid可用于被動(dòng)語態(tài)，let偶爾也可用于被動(dòng)態(tài)，用作主語補(bǔ)足語的動(dòng)詞不定式通常帶to，但在make和let后有時(shí)可以不帶to
(1)John was made to wash the truck for a week as a punishment.
(2)He was made(to) laugh.
(3)The child was let(to) do it.
五、never與know連用其后作賓語補(bǔ)足語的動(dòng)詞不定式可省to，其時(shí)態(tài)多為完成時(shí)態(tài)。
(1)I never knew him act without thinking.
(2)I've never known it snow in July before.
(3)I had never known her ask for pity before.
有時(shí)ever與known連用也有上述用法。
(1)Have you ever known me tell a lie?
六、在find后作賓語補(bǔ)定語的動(dòng)詞不定式有時(shí)可以省to，但如動(dòng)詞為be，那么一般不省to，要省一起省略"to be"
(1)We found the farm crops(to) do well.
(2)I find the Chinese people to be happy and cheerful.
(3)I found this to be true in all the cities.
(4)We found him (to be) honest/dishonest.
七、在cannot but,cannot help but,can not choose but, had better(best),would(had) rather(sooner)…than…, would as soon…as…后的動(dòng)詞不定一般不帶to
(1)When the country calls you for help,you cannot but go.
(2)He can't help but feel sorry for her.
(3)he cannot choose but obey.
(4)I had better leave now,or I'll be late.
(5)He had best buy it now while it is still available.
(6)I would rather go mountain—climbing than just take a walk.
(7)My aunt invited me to the movies,but I said I had rather go on a picnic with the girls.
(8)I had sooner live on a farm than in the city.
(9)He would sooner resign than take part in such dishonest business deeds.
(10)I'd rather not tell you.
(11)He said he'd sooner die than betray his friend.
八、在but(=except),besides,than后的動(dòng)詞不定式一般要帶to，但如果其前有作謂語的實(shí)義動(dòng)詞do，則不定式不帶to
(1)The soldier has no choice but to obey.
(2)He did not have any choice but to obey.
(3)She did nothing but clean the dishes.
(4)The children found there was nothing they could do with their money,except spend it on sweets.
(5)There seemed nothing else to do but(to)send for a doctor.(but前的實(shí)義動(dòng)詞do不作謂語，but后的不定式可帶to，也可不帶to)
(6)He did nothing else than laugh.
(7)I could hardly do less than wait.
九、不定式作表語時(shí)，如主語部分含有實(shí)義動(dòng)詞do，且句子的時(shí)態(tài)為一般現(xiàn)在時(shí)或一般過去時(shí)(多為is或was)，不定式可以帶to也可不帶to
(1)What we must do now is(to) find anther person to help us.
(2)All he could do was (to) rush into the room.
如句子的動(dòng)詞時(shí)態(tài)不是一般現(xiàn)在時(shí)或一般過去時(shí)，作表語的動(dòng)詞不定式一般要帶to
(1)She knew that all she would have to do would be to stop crying.
十、rather than位于句首時(shí)，其后用不帶to的不定式，但rather than在句中時(shí)，其后的動(dòng)詞不定式可以帶to，也可以不帶to
(1)Rather than ride on a crowded bus,he always prefers to ride a bicyde.
(2)Rather than cause trouble,he left.
(3)He prefers to rent a car rather than(to) have one of his own.
十一、在動(dòng)詞help后作賓語補(bǔ)足語的動(dòng)詞不定式可以帶to，也可以不帶，在英國英語中，多用不帶to的不定式，但在英國英語中，help+賓語+不定式結(jié)構(gòu)中，用不帶to的不定式表示主語直接參與不定式的表示的動(dòng)作，用帶to的不定式表示主語沒有直接參與不定式的表示的動(dòng)作。
(1)He helped me repair the bicycle.
(2)He helped me to repair the bicycle.
(3)This kind of soap helps us to wash the clothes more easily.
(4)The book will help you to study English.
但在被動(dòng)語態(tài)中，help后的不定式要帶to(1)She was helped to repair her bicycle.
在help(to) do sth不定式符號to可省略。
He helped(to) repair the machine.
十二、兩個(gè)或兩個(gè)以上的動(dòng)詞不定式并列在一起時(shí)，第一個(gè)不定式帶to，后面的不定式一般省去to
(1)Her job is to take care of the children and wash clothes.
(2)The girl doesn't know how to read and write.
但如果是在對照場合，則不省去to
(1)It is better to laugh than to cry.
(2)The purpose of new technologies is to make life easier,not to make it more difficult.
十三、than連接兩個(gè)動(dòng)詞 不定式?jīng)]有對比關(guān)系時(shí)，后一個(gè)不定式可以省to
(1)You might do worse than(to) do as he does.
(2)I cannot do better than(to)get away for the few days.
下面句子中than連接的不是兩個(gè)動(dòng)詞不定式than后的動(dòng)詞不定式通常要帶to
(1)I know better than to believe him.
(2)The beaten enemy had no choice than to surrender.
下句中的more than(=only)可以看成復(fù)合副詞，后面的動(dòng)詞不定式不帶to
(1)I did not more than make a beginning.
十四、在why,why not后的不定式不帶to
(1)Why spend such a lot of money?
(2)Why not join us?
(3)Why don't you smoke?
十五、實(shí)義動(dòng)詞dare在現(xiàn)代英語口語中，其所在的否定句或疑問句中，它后的動(dòng)詞不定式可省to，尤其在一般過去時(shí)中
(1)Does he dare go?
(2)We do not dare speak.
(3)He did not dare go.
(4)Did he dare go?
(5)He dared go.
(6)Dared he go?
(7)He knew she dared not open his mouth.
十六、在口語中，特別是在美國，祈使語氣謂語動(dòng)詞和構(gòu)成謂語的不定式go后面的不定式往往不帶to
(1)Go ask her.
(2)I'll go see my brother.
這種用法在英國口語中比較少見，一般在動(dòng)詞go后用連詞and
(1)GO and ask her.
(2)I'll go and see my brother.
十七、在"will you please…?"和would you please…?句型中，要用不帶to的不定式。
(1)Will you please give the note to Tom?
(2)Will you please open the window?
(3)Would you please give me a hand?
十八、Better+動(dòng)原(口語中用)
(1)Better ask them go astray.
(2)Better go at once.
