完成式： 不定式的一般形式所表示的動作， 通常與主要謂語表示的動作（狀態(tài)）同時(shí)（或幾乎同時(shí)）發(fā)生， 或是在它之后發(fā)生。 假如不定式所表示的動作， 在謂語所表示的動作（狀態(tài)）之前發(fā)生， 就要用不定式的完成式。
I am glad to have seen your mother （= I am glad I have seen your mother）。
（比較： I am glad to see you.）
He is said to have written a new book about workers.
He pretended not to have seen me.
進(jìn)行式： 如果主要謂語表示的動作（狀態(tài)）發(fā)生時(shí)， 不定式表示的動作正在進(jìn)行， 這時(shí)要用不定式的進(jìn)行式。
You are not supposed to be working. You haven’t quite recovered yet.
We didn’t expect you to be waiting for us here.
He pretended to be listening attentively.
完成進(jìn)行式： 在謂語所表示的時(shí)間之前一直進(jìn)行的動作， 就要用不定式的完成進(jìn)行式。
The struggle was known to have been going for twenty years.
We are happy to have been working with you.
被動式： 當(dāng)不定式的邏輯上的主語是不定式所表示的動作的承受者時(shí)， 不定式一般要用被動形式。
It is an honour for me to be asked to speak here.
She hated to be flattered.
He wanted the letter to be typed at once.
This is bound to be found out.
There are a lot of things to be done.
She was too young to be assigned such work.
功用： 不定式可以作主語 （a）， 賓語 （b）， 表語 （c）， 定語 （d） 或是狀語 （e）。
a. To scold her would not be just.
b. We are planning to build a reservoir here.
c. One of our main tasks now is to mechanize agriculture.
d. Do you have anything to declare？
e. We have come to learn from you.
不帶to 的不定式：
在“動詞+ 賓語+不定式”結(jié)構(gòu)中， 如果動詞是表示感覺意義的see， hear， watch， smell， feel， notice等， 或是表示“致使”意義的 have， make， let等， 其后的不定式結(jié)構(gòu)不帶to.
John made her tell him everything.
這類結(jié)構(gòu)轉(zhuǎn)換為被動語態(tài)時(shí)， 后面的不帶to 的不定式一般還原為帶to 的不定式。
She was made to tell him everything.
在 had better， had best， would rather， would sooner， would just as soon， might （just） as well， cannot but 等搭配之后， 動詞不定式也不帶to.
I’d rather not have eggs and bacon for breakfast.
They cannot but accept his term.
在make do， make believe， let drop， let fall， let fly， let slip， let drive， let go of， let there be， hear say， hear tell， leave go of等固定搭配中， 用不帶to的動詞不定式。
John let fly a torrent of abuse at me.
I’ve heard tell of him.
在動詞help（或help +賓語）之后可用不帶to的不定式， 也可用帶to的不定式。
Can I help （to） lift this heavy box？
在介詞except， but 之后， 如果其前有動詞do的某種形式， 不定式一般不帶to， 反之帶to.
I am glad to have seen your mother （= I am glad I have seen your mother）。
（比較： I am glad to see you.）
He is said to have written a new book about workers.
He pretended not to have seen me.
進(jìn)行式： 如果主要謂語表示的動作（狀態(tài)）發(fā)生時(shí)， 不定式表示的動作正在進(jìn)行， 這時(shí)要用不定式的進(jìn)行式。
You are not supposed to be working. You haven’t quite recovered yet.
We didn’t expect you to be waiting for us here.
He pretended to be listening attentively.
完成進(jìn)行式： 在謂語所表示的時(shí)間之前一直進(jìn)行的動作， 就要用不定式的完成進(jìn)行式。
The struggle was known to have been going for twenty years.
We are happy to have been working with you.
被動式： 當(dāng)不定式的邏輯上的主語是不定式所表示的動作的承受者時(shí)， 不定式一般要用被動形式。
It is an honour for me to be asked to speak here.
She hated to be flattered.
He wanted the letter to be typed at once.
This is bound to be found out.
There are a lot of things to be done.
She was too young to be assigned such work.
功用： 不定式可以作主語 （a）， 賓語 （b）， 表語 （c）， 定語 （d） 或是狀語 （e）。
a. To scold her would not be just.
b. We are planning to build a reservoir here.
c. One of our main tasks now is to mechanize agriculture.
d. Do you have anything to declare？
e. We have come to learn from you.
不帶to 的不定式：
在“動詞+ 賓語+不定式”結(jié)構(gòu)中， 如果動詞是表示感覺意義的see， hear， watch， smell， feel， notice等， 或是表示“致使”意義的 have， make， let等， 其后的不定式結(jié)構(gòu)不帶to.
John made her tell him everything.
這類結(jié)構(gòu)轉(zhuǎn)換為被動語態(tài)時(shí)， 后面的不帶to 的不定式一般還原為帶to 的不定式。
She was made to tell him everything.
在 had better， had best， would rather， would sooner， would just as soon， might （just） as well， cannot but 等搭配之后， 動詞不定式也不帶to.
I’d rather not have eggs and bacon for breakfast.
They cannot but accept his term.
在make do， make believe， let drop， let fall， let fly， let slip， let drive， let go of， let there be， hear say， hear tell， leave go of等固定搭配中， 用不帶to的動詞不定式。
John let fly a torrent of abuse at me.
I’ve heard tell of him.
在動詞help（或help +賓語）之后可用不帶to的不定式， 也可用帶to的不定式。
Can I help （to） lift this heavy box？
在介詞except， but 之后， 如果其前有動詞do的某種形式， 不定式一般不帶to， 反之帶to.