這很簡(jiǎn)單.句子陳述的對(duì)象就是主語(yǔ)；動(dòng)詞的對(duì)象（或內(nèi)容）就是賓語(yǔ)；凡是修飾名詞的都是定語(yǔ).如：
This is the book （that/which) I want to buy.這是我想要買的書(shū).
that/which是買的對(duì)象,作賓語(yǔ).關(guān)系詞如果在從句中作賓語(yǔ),可以省略.
I saw a man who/that was wearing a red coat.我看見(jiàn)一個(gè)穿紅上衣的男人.
who/that在從句中作主語(yǔ).
I saw a man whose coat was red.我看見(jiàn)一個(gè)穿紅上衣的男人.
whose修飾coat,是定語(yǔ).
作主語(yǔ)、賓語(yǔ)或定語(yǔ)的關(guān)系詞叫關(guān)系代詞.
如果關(guān)系詞在從句中表示的是時(shí)間、地點(diǎn)、原因等,就是狀語(yǔ).如：
Do you remember the day when we played together?你記得我們一起玩的日子嗎?
when在從句中表示時(shí)間,是時(shí)間狀語(yǔ).
The reason why he was late is that he didn't get up early.他遲到的原因是他沒(méi)有早起.
why在從句中作原因狀語(yǔ).
作狀語(yǔ)的關(guān)系詞叫關(guān)系副詞.