⒉ 不定式在句中作某些动词后的宾补或主补时，常见的有ask, tell, advise, force, persuade, wish, allow, permit等。

如：She wants to come but her parents won't allow to.

⒊ 不定式在句中作某些形容词的状语时，常见形容词如happy, glad, eager, anxious, willing, ready等。

如：I think she should get a job, but you can't force her to if she's not ready to

-I'll be away on a business trip. Could you mind looking after my cat?

-Not at all. I'd be happy to.

⒋ 不定式作某些复合谓语时，常见结构如be able to, be going to , have to, ought to, used to等。

如：He doesn't like fish but he used to.

注意,当省略的内容是作动词用的have或be的任何形式时,to 后面保留原形have或be.

如：He didn't come, but he ought to have.

Alice is not what she used to be.

动词不定式符号to 的省略

⒈ 主语部分有to do, 系动词是 is或was时，作表语的不定式通常省略to.

如：The only thing you have to do is (to) press the button.

⒉ 作介词but, except, besides的宾语时，前面有实义动词do时，常省略不定式符号to.

Tom had nothing to do besides answer betters this morning.

⒊ 当两个或多个不定式并列时，其后的不定式符号可省略，但有对比关系时则不省略。

如：It is easier to make a plan than to carry it out.

⒋ 在see, watch, notice, hear, listen to, look at, feel, have make, let, leave, observe等词后作宾语补足语时，省略不定式符号to；Why (not)do结构中不定式不带to.

如：Did you notice her enter the room?

why not join us?

介词的省略

⒈ 一些常和动名词、形容词一起搭配的介词常省略，而保留其后的 动名词，常见的句型有spend/waste time(in)doing, lose no time(in)doing, have difficult/trouble (in) doing, be busy (in) doing, stop/prevent sb. (from) doing 等。

如：The heavy rain prevented him (from) arriving there on time.

She lost no time(in) giving the patient first aid.

⒉ 表示时间的介词at, on和in 用在next, last, this, these, yesterday, tomorrow, one, any, every, each, some, all等词之前，一般皆省略，表示一段时间状语之前的for 也可省略。