whether和if的用法區(qū)別 1)whether和if常用來(lái)引導(dǎo)賓語(yǔ)從句,這時(shí)兩者的含義區(qū)別很小,一般可通用.例如：①I(mǎi) don't know whether/if they will come to help us.我不知道他們是否來(lái)幫助我們.②I am not sure whether/if I'll have time to go with you.我很難說(shuō)我們是否有時(shí)間跟你們一起去.上面兩句無(wú)區(qū)別.但是,當(dāng)whether與or not連成一個(gè)詞組時(shí),whether不可換用if.例如：③I don't know whether or not they will come for our help.我不知道他們是否要來(lái)求我們支援.【注意】若whether和or not不連在一起,在日語(yǔ)中可以用if取代whether,當(dāng)然也可以用whether.例如：④I am not certain if/whether the train will arrive on time.我沒(méi)有把握火車是否準(zhǔn)時(shí)到達(dá).⑤I don't care if/whether your car breaks down or not.我不在乎您的車是否是會(huì)出故障.此外,還有三種情況值得注意：(1)在介詞后面只能用whether,不能用if.例如：①This depends upon whether we are determined to do it.這件事要看我們是否有決心去做.②It depends on whether he is ready.這件事要看他是否有準(zhǔn)備.③I am not interested in whether you'll come or not.你來(lái)不來(lái)我不感興趣.④We haven't settled the question of whether we'll renew our supplies of coal for factory.是否要為我們工廠補(bǔ)充一些煤,這個(gè)問(wèn)題我們還沒(méi)有決定.(2)在動(dòng)詞不定式之前,只能用whether,不能用if.例如：①He doesn't know whether to stay or not.他不能知道是否要留下來(lái).②She doesn't knows whether to get married now or wait.是否現(xiàn)在結(jié)婚或是等待她不知道.(3)在及物運(yùn)動(dòng)discuss后的賓語(yǔ)從句中,只能用whether,不能用if.例如：①We discussed whether we should make a change in our plan.我們討論了是不是要對(duì)我們的計(jì)劃作一些修改.②We were discussing whether we should discuss the business with them.我們正在討論我們是否要和他們談這個(gè)生意.2)引導(dǎo)主語(yǔ)從句時(shí),只能用whether,不能用if.例如：①I(mǎi)t is unknown whether he will come.他是否來(lái)還不知道.②Whether the news is true remains a question.這個(gè)消息是否真實(shí)仍然是個(gè)問(wèn)題.3)引導(dǎo)表語(yǔ)從句時(shí),只能用whether,不能用if.例如：①What we want to know is whether he will come to speak to us tomorrow.我們想知道的是他明天是否來(lái)給我們講話.②The question is whether they can take our advice.問(wèn)題是他們是否能接受我們的意見(jiàn).4)引導(dǎo)同位語(yǔ)從句時(shí),常用whether.例如：①The question whether we'll build another lecture building hasn't been settled.是否要另建一幢教學(xué)樓的問(wèn)題還未決定.②The question whether he'll come is unknown.他是否來(lái)的問(wèn)題還不知道.5)可以用來(lái)引導(dǎo)一個(gè)否定的賓語(yǔ)從句,whether則不能用來(lái)引導(dǎo)否定的賓語(yǔ)從句,因?yàn)樗硎菊磧煞矫娴倪x擇意義比較強(qiáng).例如：①Tell me if it is not going to rain,please.請(qǐng)告訴我明天是否不會(huì)下雨.②He considered if he shouldn't tell her the secret.他考慮他是否不該告訴她這個(gè)秘密.6)if除引導(dǎo)賓語(yǔ)從句外,還可以引導(dǎo)條件狀語(yǔ)從句,作“是否”解.在容易引起混淆產(chǎn)生歧義的情況下,就不可用if,而須用whether.例如：①Please let me know if you intend to come.這個(gè)句子有兩種解釋：A：“請(qǐng)讓我們知道你是否想來(lái).” B：“如果你打算來(lái),請(qǐng)讓我們知道.” 第一種解釋是把if引導(dǎo)的從句看作賓語(yǔ)從句,把動(dòng)詞know視為及物動(dòng)詞(vt．)；第二種解釋是把if引導(dǎo)的從句當(dāng)作條件狀語(yǔ)從句,把動(dòng)詞know看作不及物動(dòng)詞(vi．).在口語(yǔ)中,我們可以通過(guò)語(yǔ)調(diào)來(lái)表示兩者的區(qū)別；但是,在書(shū)面語(yǔ)中,無(wú)上下文(如一張便條上寫(xiě)著這句話),那就含混不清了.如果我們想表達(dá)的第一種含義,就得用whether來(lái)改寫(xiě)第一句.①Please let me know whether you intend to come.又如：②Let me know whether he has left for Shanghai.告訴我他是否已經(jīng)去上海了.③Let me know if he has left for Shanghai.如果他去上海,請(qǐng)告訴我一聲.