为了避免重复，使语言简练紧凑，在不损害句子结构或引起误解的情况下，往往省略一个或多个句子成分或词语。
I.简单句中的省略
(1)不定式“to”的省略
(2)所有格之后的名词为“住宅、商店、I矿、门诊、教堂"等时，可以省略
She’s going to the barber’s.
I happened to meet him at the tailor’s(shop).
(3)独立主格结构中分词。如果为“being”或“having been”时可以省略。
The meeting(being)over，we all left the room.
Tools(having been)carried，we went on our way to the fields.
(4)感叹句中的省略：
What a day (it is)!
What a pretty girl (she is)!
How beautiful!
(5)表示某种性质的介词“口’用于疑问代词"what"之前可以省略o
(Of) what trade is he?
(Of)What size is your coat?
(6)祈使句中的主语省略：
(You)Name three different kinds of matter.
(You)Work hard next time，and you will succeed.
(You)Use your head，and you will find a way.
Ⅱ.并列句中的省略
(1)在并列句中，后一个句子有时可以省略跟前面句子中相同的部分
Matters consist of molecules，and molecules(consist)d atoms.
Tom is writing his term paper，but John isn’t(writing his term paper).
We frequently regard gases as compressible，(and regard)liquids as incompressible.(我们通常把气体看成是可以压缩的，液体是不可压缩的。)
(2)在并列句中，第二句用"neither/nor/so"引出时，出现省略;“neither/nor/so还可以引起倒装。
He didn’t fear new ideas，nor did he fear the future.
试比较
“I went to the movie last night.”一————“So did I ”
“Did Alice learn Spanish in high school?”一——“I think so ”
Ⅲ.从句中的省略
(1)宾语从句中的省略：
1)以“which/where/when/how/why”等引起的宾语从句，在其谓语动词与主句谓语动词相同时，其后的主语和谓语可全部省略，而仅保留一个"wh-"词。
She can’t come，but 1 wonder why(she can’t come).
He will be back，I don’t know when(he will be back).
Please hand me one of those books，I don’t care which(you hand me).
2)在“I’m afraid，I believe，I expect，I fancy，I fear，I hope，I imagine，I should，I should say，I suppose，I think，I trust”之后的"not"等于一个否定的"that"从句，“so”等于一个肯定的"that"从句。
“Is he sick”一“I am afraid so.”(=I am afraid that he is sick.)
“Will it rain tomorrow?"一“I hope not.”(=I hope that it will not rain tomorrow.)
