英语if的用法总结

if的用法：表示条件，意思是如果；表示虚拟，意思是假如；表示是否的含义，和whether相同用法，连接宾语从句。

扩展资料

1.(表示条件)如果 ,主句用将来时,if从句用现在时表示将来

He will come if you invite him.

如果你请他,他会来的`.

2.(表示虚拟)假如,要是

时态：可以表示过去,现在和将来的情况.它的基本特点是时态退后.

a.同现在事实相反的假设.

句型：条件从句主句

一般过去时 should( would) +动词原形

If they were here,they would help you.

b.表示于过去事实相反的假设.

句型：条件从句主句

过去完成时 should(would) have+ 过去分词

If she had worked harder,she would have succeeded.

The rice would not have been burnt if you had been more careful.

If my lawyer had been here last Saturday,he would have prevented me from going.

If he had come yesterday,I should / would have told him about it.

含义：He did not come yesterday,so I did not tell him about it.

If he had not been ill and missed many classes,he would have made greater progress.

含义：He was ill and missed many lessons,so he did not make greater progress.

c.表示对将来的假想

句型：条件从句主句

一般过去时 should+ 动词原形

were+ 不定式 would + 动词原形

should+ 动词原形

If you succeeded,everything would be all right.

If you should succeed,everything would be all right.

If you were to succeed,everything would be all right.

3.是否 = whether 连接宾语从句

I wonder if she is ill.

不知她是否病了.

英语as as用法总结......

“as(否定句中可用so)+adj./adv.+as…”，其基本意思为“……和……一样”。但在实际应用中，此结构在不同的语境中含义差异较大。as…as结构的另一种形式是“as much/many+名词......

or为并列连词,含有选择意义,必须连接同等成分的词、短语或句子,并使用同一种形式。or连接两个或两个以上的单数名词作主语时,谓语动词要用单数; 如果or连接的两个主语是两个......

介词by可以用来表示方位、时间、手段等。by的意思是靠近，通过，作介词时表示在……之前。扩展资料by的用法归纳一、by+地点名词。表方位，意为：“在…旁边”。例句：Our teacher was......

of用作介词，表示在…的,在…之前;由于,因为；用...做成的；在…方面等含义；可表示同位，表示主格关系。扩展资料1、(表示时间)在…的`,在…之前; 在…期间What do you do of a Satu......