1． 不定式（to do）是由动词转化而来的一种形式，仍保留有动词的特征：
○1有自己的宾语和状语。不定式与自己的宾语和状语构成不定式短语。
○2有时态和语的变化，但它是非谓语动词，不能做谓语，可作除谓语
以外的成份：主、宾、表、定、状、补。
2． 时态和语态：
语态 时态 主动语态 被动语态
一般式 to do to be done
完成式 to have done to have been done
进行式 to be doing
(注)进行式(to be doing)常用在如下动词后：seem, appear, happen,
think, consider, pretend, want等。
Eg. He happened to be sleeping when I went into the room.
◆时态：○1一般式：不定式动作与谓语动作（几乎）同时发生，
或发生在谓语动作之后。
○2完成式：不定式动作发生在谓语动作之前。
○3进行式：谓语动作发生时，不定式动作正在进行。
Eg. I’m glad to see you.
I’m glad to have received your letter.
He pretended to be sleeping.
◆语态：vi.不定式只有主动语态，无被动语态。
vt. 不定式有主被动语态。
不定式的逻辑主语是不定式协作的执行者，要用主动语态。
不定式的逻辑主语是不定式协作的受动者，要用被动语态。
eg. I’m glad to meet you.
He disliked to be praised in public.
3． 句法功能：
1） 作主语：To smoke is a bad habit.(不定式作主语，谓语动词用单数）
不定式短语作主语时通常后置，而用it作形式主语，
且常构成以下句型：
It+be+adj./n.+to do
It+be+adj./n.+ for sb.+to do eg. It’s nice of you to help me.
of It’s important for me
to learn English.
It takes/took sb. time to do
It costs/cost sb. money to do.
2)作宾语，接不定式作宾语的动词：
agree, decide, hope, manage, plan, prepare, pretend, promise,
refuse, want, wish.
begin/start/like/love/hate/continue/prefer +to do 意思差别不大。
doing
like to do具体的一次性的动作。
like doing 习惯性的动作
eg. I like watching TV, but I don’t like to watch TV today.
stop to do remember to do
doing doing
forget to do go on to do
doing doing
try to do mean to do
doing doing
eg. Waving one’s hand means saying “Goodbye”.
Don’t be angry with Tom. He doesn’t mean to hurt you.
I remember _____ the windows, so you don’t have to do it.
I remember_____the windows, so I’ll do it at once.
3）作宾语补足语：
He advised me to stop smoking.
V． + 宾语 + 宾补
作宾语补足语的不定式有时可以省to，主要包括以下动词：
A． 使役动词：make, let, have,（let, have不用于被动语态）
B． 感官动词：see, hear, notice, feel, watch, look at, listen to, find,但被动语态
要加上to.
C． help后可省可不省to: help sb. (to) do
4)定语：放在n./pron.之后
eg. She has a lot of work to do.
（注）○1不定式中的动词如不及物，后应加上适当的介词
Eg. Have you enough paper to write on?
She is a very nice person to work with.
○2there are句型中的不定式（to do）作定语，可用主动或被动。
eg. There be a meeting to attend.
to be attended
5）状语： in order to do
○1目的状语： so as to do
to do
○2结果状语： only to do eg. He woke up only to find he
was locked in the room.
too+adj.+to do
enough to do eg. He is old enough to go to school.
6）表语：His wish is to be an artist.
4．其它注意事项：
1）否定式：not to do eg. I’m sorry not to have accepted your advice.
2）不定式可用主动形式表示被动意义的情况：
○1当不定式的逻辑主语以动作执行者的身份出现在句中时：
Eg. Parents should give the children some housework to do.
○2“be+ adj.+to do”
eg. The result is hard to tell.
The book is interesting to read.
○3There be结构中，作定语的不定式可用主动也可用被动形式。
eg. There are many goods to ship in the port.
○4be to blame习惯用法中：
eg. I’m to blame for this. 我为此将受到谴责。
This house is to let. 这房子要出租。
3）for/of sb. to do 叫做不定式的复合结构。
4）wh- + to do 叫做带特殊疑问词的不定式，常放在know/show/ learn
作主、宾、表。
5）主句部分出现动词do, 表语的不定式可省to.
eg. What I want to do is run a night school.
6)but/except 前的谓语动词有do，介词后无to；前无do ，后有to
eg. I did nothing but repair my bike.
I will do anything but cook.
I have no choice but to wait.
7)and/or连接两并列的不定式时，后一个不定式可省to
eg. To leave or stay is not decided.
8）want, need, require主语是物，不是人时，后面用doing
或to be done译为“需要”
eg. The desk needs repairing to be repaired.
Your hair wants cutting/to be cut.
9）动词不定式的省略，动词可省，不定式符号“to” 不可省.