if

conj

• ①[表假设、条件]如果,假设,倘若1[使用现在式述语动词,推测现在或未来的不确定事项]2[使用过去式,表达与现在的事实相反的假设,表结论的主要子句通常使用would, should等助动词过去形]3[使用过去完成式,表达与过去事实相反的假设,主要子句要使用would, should等助动词过去形+完成式]4[不论人称,一律使用should对未来作可能性很少的假设]万一…的话5[表未来的纯粹假设](★if子句中用were to)
  • We'll stay at home if it rains tomorrow.如果明天下雨,我们就待在家里。
  • If you are tired, you may take a rest.如果你累了,可以休息一下。
  • If nothing else, the work improves my French.如果说这工作没有其他好处,它至少使我的法文进步。
  • If you have finished your work, you may go home.如果你完成了工作,你可以回家。
  • If he said so, he was a liar.如果他这么说,他是个说谎者。
  • I'll be hanged [damned] if I go.【口】我死也不去。
  • Do you mind if I smoke?我抽烟你不在意吧?
  • If you will help, we'll [we shall] be successful.如果你肯帮助,我们会成功的(★条件句表意志)。
  • I shall tell her if she comes.如果她来了,我就跟她说。
  • If I knew the answer, I would tell you.如果我知道答案,我就会告诉你。
  • If I were you, I would tell her.如果我是你的话,我就会告诉她。
  • If I had known, I wouldn't have gone.我如果知道的话,就不会去了。
  • If he had listened to me, he wouldn't be in such trouble now.假如(当时)他听我的话,他现在就不会处于这种困难(★此句的条件句表与过去事实相反,主要子句则表与现在事实相反)。
  • If it should rain tomorrow, I shall not [shan't, won't] go.万一明天下雨,我就不去了(If it rains tomorrow, ...表单纯的预料)。
  • If she were to leave you tomorrow, what would you do?假定明天她离开你,你要怎么样?

• ②[表让步]即使,纵令(=even though)
  • If he be ever so rich ...【古】即使他很富有…
  • I will do it if it kills me.即使这会要我的命,我也要做。
  • If he noticed the fact, he didn't care.就算他注意到这项事实,他也不介意。
  • The rooms were beautifully if quietly furnished.房间陈设虽朴素,但很雅致。
  • Even if you do not like it, you must eat it.(★强调形为even if)即使你不喜欢,也得吃。
  • I'll go even if it rains.即使下雨,我也要去。

• ③ 每次…时(=whenever)
  • If I feel any doubt, I ask.我一有疑问就问。

• ④[引导间接疑问句]【口】是否…(=whether)
  • Try [Ask her] if it is true.试试[问她]看是不是真的。
  • I wonder if she's at home [whether she's at home or not].我不知道她是否在家。(★if与whether不同,后面不能接不定词)

• ⑤[省略结论子句的感叹句,表惊愕、愿望等]
  • If I only knew!=If only I knew!要是我知道就好了!(可用how happy I should be等来补充)
  • If I haven't lost my purse!要是我没丢了钱包,那该多好!(前面可补充I'm blessed等)