1.不定式定義:由to＋動詞原形構(gòu)成.
不定式是一種非限定性動詞.而非限定動詞是指那些在句中不能單獨充當(dāng)謂語的動詞,可分為不定式,動名詞,現(xiàn)在分詞和過去分詞.
2.用途：
在句中不能作謂語.它具有動詞的性質(zhì),本身可以帶賓語和狀語.
【動詞不定式】
1.定義：動詞 + 不定式
2.用途：
動詞不定式在句中可以作句子任何成分.動詞不定式的被動形式除了一般形式外還有其完成式和進(jìn)行式.
[編輯本段][動詞不定式的時態(tài)、語態(tài)]
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(dá)的意義是動作,這一動作一定由使動者發(fā)出.這一使動者我們稱之為 邏輯主語,其形式如下：
主動形式 被動形式
一般式 （not） to make （not） to be made
完成式 （not） to have made （not） to have been made
進(jìn)行式 （not） to be making
完成進(jìn)行式 （not） to have been making
(1)語態(tài)
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(tài)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(jié)構(gòu)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 t ake care of (to be taken care of).但有時兩種形式表達(dá)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.)
(2)時態(tài)
1) 現(xiàn)在時：一般現(xiàn)在時表示的動詞,有時與謂語動詞表示的動作同時發(fā)生,有時發(fā)生在謂語動詞的動作之后.
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) 完成時：表示的動作發(fā)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(jìn)行時：表示動作正在進(jìn)行,與謂語動詞表示的動作同時發(fā)生.
He seems to be eating something.
4) 完成進(jìn)行時：
She is known to have been wreaking on the problem for many years.
[編輯本段][疑問詞＋不定式結(jié)構(gòu)]
疑問詞who,what,which,when,where,whether,how后可接不定式構(gòu)成不定式短語,在句中作主語、賓語、表 語等.如：
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.（不定式在句子中做間接賓語）
④The question was where to get the medicine needed.（不定式在句子中表語）
以上例句中疑問詞＋不定式部分,均可轉(zhuǎn)換為相應(yīng)的從句形式.如：①When we shall leave…③…h(huán)ow I
could learn…
經(jīng)常在這種結(jié)構(gòu)中使用的動詞有：consider,decide,discover,explain,find out,forget,hear,know,lea rn,observe,understand,wonder等.
[編輯本段][動詞不定式的語法功能]
一、作主語
動詞不定式作主語時,句子的謂語動詞常用單數(shù),其位置有以下兩種：
(1)把不定式置于句首.如：
To get there by bike will take us half an hour.
(2)用it作形式主語,把真正的主語不定式置于句后,常用于下列句式中.如：
①It＋be＋名詞＋to do
It's our duty to take good care of the old.
②It takes sb+some time+to do
How long did it take you to finish the work?
③It＋be＋形容詞＋for sb＋to do
It is difficult for us to finish writing the compositionin a quarter of an hour.
④It＋be＋形容詞＋of sb＋to do
It is stupid of you to write down everything the teachersays.
⑤It seems(appears)＋形容詞＋to do