when 既可引導(dǎo)限制性定語(yǔ)從句，又可引導(dǎo)非限制性定語(yǔ)從句。先行詞是時(shí)間名詞，在從句中充當(dāng)時(shí)間狀語(yǔ)，相當(dāng)于“介詞+which”。如：
Can you tell me the time when the film will start?—Can you tell me the time at which the film will start? 請(qǐng)告訴我電影什么時(shí)候開(kāi)始好嗎?(限制性定語(yǔ)從句)
I will never forget the day, when I joined the Party. —I will never forget the day, on which I joined the Party. 我入黨的那一天，我永遠(yuǎn)不會(huì)忘記。(非限制性定語(yǔ)從句)
關(guān)系副詞where的用法
where既可引導(dǎo)限制性定語(yǔ)從句，又可引導(dǎo)非限制性定語(yǔ)從句。先行詞是地點(diǎn)名詞，在從句中充當(dāng)?shù)攸c(diǎn)狀語(yǔ)，相當(dāng)于：“介詞+which”。如：
This is the school where I studied a few years ago. —This is the school in which I studied a few years ago. 這就是我?guī)啄昵八谧x書(shū)的學(xué)校。
Let’s go to the concert, where you will find much fun. —Let’s go to the concert, in which you will find much fun. 我們?nèi)ヒ魳?lè)演唱會(huì)吧，在那里你會(huì)找到很大的樂(lè)趣。
關(guān)系副詞why的用法
why只能引導(dǎo)限制性定語(yǔ)從句，先行詞只有reason一詞，在從句中充當(dāng)原因狀語(yǔ)，相當(dāng)于：“for + which”。如：
Do you know the reason why he is not here now?—Do you know the reason for which he is not here now? 你知道他還沒(méi)有來(lái)這兒的原因嗎?
關(guān)系副詞that的用法
that只能引導(dǎo)限制性定語(yǔ)從句，充當(dāng)關(guān)系副詞時(shí)，其作用相當(dāng)于：“介詞+關(guān)系代詞”，在從句中充當(dāng)時(shí)間、地點(diǎn)、方式、原因狀語(yǔ)等。如：
1. 在定語(yǔ)從句中作時(shí)間狀語(yǔ)�，F(xiàn)行詞有：each time, every time, anytime, the first time, the moment, the minute, the hour, etc. 但現(xiàn)代英語(yǔ)中，that往往省略。如：
Each time (that) I meet him, he will smile and say “hello”. 每次我會(huì)見(jiàn)他時(shí)，他都會(huì)笑著說(shuō)“喂，你好!”
2. 在定語(yǔ)從句中作方式狀語(yǔ), 現(xiàn)行詞是way, 如：
Can you show me the way (that) you solve the problem like this? 請(qǐng)告訴我你解決這類問(wèn)題的方法好嗎?
3. 在定語(yǔ)從句中作原因狀語(yǔ)，現(xiàn)行詞只有reason一詞，如：
I don’t know the reason (that) he has left school now. 我不知道他輟學(xué)的原因。
4. 在定語(yǔ)從句中做其他狀語(yǔ)，現(xiàn)行詞如price, speed等，如：
I think the price (that) she sells her apple is too high. (that = at which) 我認(rèn)為她賣(mài)蘋(píng)果的價(jià)格太高。
