1． 不定式（to do）是由動詞轉化而來的一種形式，仍保留有動詞的特征：
○1有自己的賓語和狀語。不定式與自己的賓語和狀語構成不定式短語。
○2有時態和語的變化，但它是非謂語動詞，不能做謂語，可作除謂語
以外的成份：主、賓、表、定、狀、補。
2． 時態和語態：
語態 時態 主動語態 被動語態
一般式 to do to be done
完成式 to have done to have been done
進行式 to be doing
(注)進行式(to be doing)常用在如下動詞后：seem, appear, happen,
think, consider, pretend, want等。
Eg. He happened to be sleeping when I went into the room.
◆時態：○1一般式：不定式動作與謂語動作（幾乎）同時發生，
或發生在謂語動作之后。
○2完成式：不定式動作發生在謂語動作之前。
○3進行式：謂語動作發生時，不定式動作正在進行。
Eg. I’m glad to see you.
I’m glad to have received your letter.
He pretended to be sleeping.
◆語態：vi.不定式只有主動語態，無被動語態。
vt. 不定式有主被動語態。
不定式的邏輯主語是不定式協作的執行者，要用主動語態。
不定式的邏輯主語是不定式協作的受動者，要用被動語態。
eg. I’m glad to meet you.
He disliked to be praised in public.
3． 句法功能：
1） 作主語：To smoke is a bad habit.(不定式作主語，謂語動詞用單數）
不定式短語作主語時通常后置，而用it作形式主語，
且常構成以下句型：
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)作賓語，接不定式作賓語的動詞：
agree, decide, hope, manage, plan, prepare, pretend, promise,
refuse, want, wish.
begin/start/like/love/hate/continue/prefer +to do 意思差別不大。
doing
like to do具體的一次性的動作。
like doing 習慣性的動作
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）作賓語補足語：
He advised me to stop smoking.
V． + 賓語 + 賓補
作賓語補足語的不定式有時可以省to，主要包括以下動詞：
A． 使役動詞：make, let, have,（let, have不用于被動語態）
B． 感官動詞：see, hear, notice, feel, watch, look at, listen to, find,但被動語態
要加上to.
C． help后可省可不省to: help sb. (to) do
4)定語：放在n./pron.之后
eg. She has a lot of work to do.
（注）○1不定式中的動詞如不及物，后應加上適當的介詞
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）作定語，可用主動或被動。
eg. There be a meeting to attend.
to be attended
5）狀語： in order to do
○1目的狀語： so as to do
to do
○2結果狀語： 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）表語：His wish is to be an artist.
4．其它注意事項：
1）否定式：not to do eg. I’m sorry not to have accepted your advice.
2）不定式可用主動形式表示被動意義的情況：
○1當不定式的邏輯主語以動作執行者的身份出現在句中時：
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結構中，作定語的不定式可用主動也可用被動形式。
eg. There are many goods to ship in the port.
○4be to blame習慣用法中：
eg. I’m to blame for this. 我為此將受到譴責。
This house is to let. 這房子要出租。
3）for/of sb. to do 叫做不定式的復合結構。
4）wh- + to do 叫做帶特殊疑問詞的不定式，常放在know/show/ learn
作主、賓、表。
5）主句部分出現動詞do, 表語的不定式可省to.
eg. What I want to do is run a night school.
6)but/except 前的謂語動詞有do，介詞后無to；前無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連接兩并列的不定式時，后一個不定式可省to
eg. To leave or stay is not decided.
8）want, need, require主語是物，不是人時，后面用doing
或to be done譯為“需要”
eg. The desk needs repairing to be repaired.
Your hair wants cutting/to be cut.
9）動詞不定式的省略，動詞可省，不定式符號“to” 不可省.