1．不定式的基本形式與結構
動詞不定式指通常由to加上動詞原形 (如to write) 所構成的一種非限定性動詞形式，但在有些情況下to可以省略。動詞不定式有進行體和完成體(如上to be writing，to have written)，也有被動態(如to be written)，所有的主動詞，不論是及物動詞還是不及物動詞，也不論是動作動詞還是狀態動詞，都有不定式形式。助動詞除be和have外， 沒有不定式形式。動詞不定式在語法功能上可作主語、賓語、表語、定語和狀語。
2．不定式的用法
1)不定式結構作主語
get contact with his family in Taiwan made him extremely happy since they separated more than 40 years ago．
finish that task in such a short time is really a challenge．
在上述情況下，如果不定式較長，顯得頭重腳輕，則可由代詞讓作形式主語(形式主語it不可由that或this等其他代詞代替)，而將不定式放到後面。如：
made him extremely happy to get contact with his family in Taiwan since they separated more than 40 years ago． admitted that it is always difficult for him to be on time．
不定式結構所表示的動作是誰做的，即不定式的邏輯主語，通常可以通過for sb. to do sth. 結構表達： is quite important for us to read good books during a general review． is not difficult fot those talented students to pass the exam. 在某些形容詞(如careless，clever，considerate，foolish，good，impolite，kind， naughty，nice，silly，stupid等)作表語時，不定式後可以加of來引匯出其邏輯主語： is very kind of you to tell me the truth． is stupid of him to do such a silly thing．
3不定式作賓語 不定式作賓語有兩種：一種是及物動詞後直接跟帶to的不定式， 另一種是“及物動詞+疑問詞+帶to的不定式。
及物動詞+帶to的不定式結構: 只能跟動詞不定式的動詞，常見的有: afford， agree， aim， appear， ask， believe， care，claim，decide demand， desire， determine， expect， fail， happen， hesitate， hope， intend， learn， long， manage， offer， pretend， promise， prepare， refuse， seek， swear， undertake，want， wish等。
managed to solve the complicated problem. stranger offered to show me the way. . Smith undertook to build a new plant in South Africa.
動詞+疑問代(副)詞+不定式： 這類動詞常見的有advise， decide， find out， forget， inquire， know， learn， see， regard， remember， teach， tell， understand， wonder等。常見的疑問代(副)詞有: what， when， where， which， how， whether等。
does not know when to start. can decide whether to continue or to stop. 3.I will show you how to deal with it.
有時，不定式可由it代替，而把不定式放到後面去。這可以用這一結構表達：動詞(如find， think，consider，feel等)+it+ 形容詞+不定式。 considers it necessary to make friends with him. find it difficult to finish all the homework before 9 o’clock.
3)不定式做表語 一種情況為主語是不定式(表示條件)；表語也是不定式(表示結果)：
see is to work means to earn a living．
另一種情況為主語是以aim，duty，hope， idea，job， plan，problem， purpose，thing，wish等名詞為中心的短語，或以what引導的.名詞性從句，不定式表語對主語起補充說明作用；例如： aim is to study abroad in the near future． most important thing is to negotiate with them about the price． I want to say is to forget all the unhappy experience．
4)不定式作定語 不定式結構作名詞片語修飾語主要有三種類型：
第一種，被修飾的名詞片語是不定式的邏輯賓語。例如： e was really nothing to fear． gave me an interesting book to read． 如果不定式是不及物動詞，後面就得加相應的介詞。例如： needs a friend to play with． girl has nothing to worry about． have a strict teacher to listen to． ough the film had been on for ten minutes， I still was not able to find a chair to sit on．第二種，被修飾的名詞片語是不定式的邏輯主語；例如： you got a key to unlock the door? action to be taken is correct． e is nothing to be gained by pretending．第三種，被修飾的名詞片語是不定式的同位結構。這類名詞通常是表示企圖、努力、傾向、目的、願望、is算、能力、意向等意義的名詞：ability， attempt， effort， impulse， inclination，wish等。例如： daughter will make an even bigger effort to please her． 2.I have no wishto quarrel withyou． her of them had any inclination to do business with Mary.
5)不定式作狀語 不定式結構在句中作狀語通常都能轉換為限制性狀語從句。例如作原因狀語： are quite surprised to see the great changes taking place in the area． are quite surprised because they see the great changes taking place in the area． was lucky to arrive before dark． was lucky because he arrived before dark．
作目的狀語： raised her voice to be heared better． raised her voice so that she could heard better． went via Heidelberg to miss the traffic jam． went via Heidelberg so that we could miss the traffic jam．
作結果狀語： French football team played so successfully as to defeat the Brazilians． French football team played so successfully that they even defeated the Brazilians． got to the station only to be told the train had gone． got to the station and was told that the train had gone．
不帶to的不定式的使用 動詞不定式通常帶to，但在有些搭配中不帶to，在另一些搭配中可帶to可不帶to。歸納起來，以下情況下使用不帶to不定式：
1) 在can／could， /may／might，will／would，shall／should，must， need，dare等情態動詞之後，動詞不定式不帶to。
2)在表示感覺意義的動詞，如see國中英語語法總結，feel，watch，notice，smell，hear，observe等後，或是表示“致使”意義的動詞，如have，let，make等後，動詞不定式不帶to。例如： 1.I often heard him say that he would study hard． 2.I must have him see his own mistakes． 但是，當這類結構轉換為被動語態時，後面的不帶to不定式一般轉換為帶to不定式。 例如： was often heard to say that he would study hard． r he had finished speaking，he was made to answer innumerable questions．
3)在動詞help之後可用不帶to的不定式，也可用帶to的不定式。例如： the old lady (to) carry the heavy box.
4) 在had better，would rather，may／might as well，rather than，can not but等搭配之後國中英語語法總結，動詞不定式也不帶to。例如： ss you feel to ill to go out，I would rather not stay at home tonight． could not but criticize his foolish behaviour.
5) 在make do，make believe，let drop，1et fall，1et fly，let slip，let drive，let go off，hear say，hear tell，leave go of等固定搭配中，用不帶to的動詞不定式。例如： let go of the rope．他們鬆開了繩子。 let fly a torrent of abuse at me．約翰朝我痛罵了一頓。 3.I've heard tell of him．我聽說過他。
6)在介詞but國中英語語法總結國中英語語法總結，except之後，如果其前有動詞do的某種形式，其後不定式一般不帶to，反之則必須帶to，表示“不得不國中英語語法總結，只能”。例如：
will do anything except work on the farm．
e was nothing left for the enemy to do but surrender．
spy was both hungry and cold；there was nothing left for him but to give in．
4.I had no choice but to wait till it stopped raining．
下面一些短語是固定搭配，不帶to： can not help but，can not choose but，can not but，do nothing but，have nothing to do but。例如： I can not but admire his courage. 如果上述句中有do，to省略： I did nothing but watch TV last night． 如果是下面一個固定搭配，就帶to： I have no choice but to give up my idea.
7)緊跟在why或why not之後的動詞不定式總是不帶to。但是，緊跟在who，what，which，whether等連線詞後的不定式帶to。例如： Why stand up if you can sit down? Why not ask your teacher when you don't understand the meaning? You needn't decide yet whether to study arts or science． 4．不定式的完成式和進行式 1)構成 完成式：to+ have done 進行式：to+ be doing
