一、指人的關係代詞。
主格——who，用在動詞前，作主語。
屬格——whose，用在名詞前作定語。
賓格——whom，用在主語、謂語動詞的前面，作動詞或介係詞的賓語。當介係詞位於句子的末尾的時候，可以用who或whom來表示，但是如果把介係詞提到從句之首，關係代詞只能用whom。
The student who answered the question was Richard.
回答這個問題的同學是約翰。
I know a boy whose mother is a doctor.
我認識一位媽媽是醫生的男孩。
The man whom she married was a teacher.
她嫁的那個人是一位教師。
The person of whom you are speaking is our principal.
你提到的那個人是我們的校長。
The person who you are speaking of is our principal.
你提到的那個人是我們的校長。
二、指物的.關係代詞。
主格——which，用在動詞前，作主語。
屬格——whose，用在名詞前作定語。
賓格——which，用在主語、謂語動詞的前面，作動詞或介係詞的賓語。我們把介係詞提前，只能用which。
English is a language which is spoken all over the world.
英語是全世界通用的語言。
Look at that house whose roof was damaged.
看那幢屋頂受損的房子。
Remember the advice which I gave you.
記住我給你的那條忠告。
The train for which I am waiting is now half an hour late.
我在等的那班火車已經晚了半小時。
三、指人或物的關係代詞。
主格——that，用在動詞前，作主語。
屬格——whose，用在名詞前作定語。
賓格——that，用在主語、謂語動詞的前面，作動詞或介係詞的賓語。
The boy that is playing the guitar is Richard.
正在彈吉他的男孩是理查德。
I like the building that was designed by Mr. Howell.
我喜歡那幢被毫爾先生設計出來的大樓。
He was looking for a car whose engine was in good condition.
他在找一輛引擎狀況很好的車子。
The sandwiches that we ate for lunch weren't delicious.
我們午餐吃的三明治不好吃。
四、其它關係代詞。
as，指前面的整個句子，可以作主語或賓語，如：
The earth is round, as is known to all.
人人皆知，地球是圓的。
The elephant is like a snake, as anybody can see.
任何人都能看見，大象就像條蛇。
than，用在比較句中，可以指代人或物。如：
You spent more money than was intended to be spent.
你花的錢超過了預定的數額。
but，表示否定，可以指代人或物。如：
There are no rules but have some exceptions.
凡規則皆有例外。
There is no mother but loves her children.
沒有哪個母親不愛自己的子女。
