英文文法之關係代名詞◎兼具代名詞與連接詞之作用的代名詞就叫做關係代名詞。
其形態如下＝＝＝＝＝＝先行詞為？主格所有格受格人who whose whom人以外之動物、事物which whose（of which）which人、動物、事物that －－－that◎應注意事項1.關係代名詞具有代名詞與連接詞的作用。
Ex：I know the man＋he came yesterday.＝I know the man who came yesterday.2.先行詞：關係代名詞所代表的名詞或代名詞就叫做先行詞。
Ex：She is the girl who wrote the letter. 其中the girl為先行詞，who為關係代名詞。
3.句中該用何種關係代名詞視其先行詞之種類而定。
Ex：the man who came here；the house which belongs to him；the dog that saved her4.關係代名詞所引導的子句叫做關係子句。
a.除了what所引導的關係子句具有名詞子句的性質外，其餘均具形容詞子句之性質。
b.關係子句的位置通常在句子的中間或句尾。
Ex：This is the boy who wants to see you.（who wants to see you 在句尾）The girl whom you saw yesterday is his sister.（whom you saw yesterday在句中）I’ll show you what I bought.（what 所引導的子句為名詞子句）5. 關係代名詞的格須視其在關係子句內的地位而定。
a. 關係代名詞若為關係子句的主詞即用主格。
b.關係代名詞若為關係子句內之動詞或介系詞的受詞即用受格。
Ex：This is the man who wants to see you.（主格）This is the man whom you want to see.（受格）Is this the book which you are looking for?（受格）I have a friend whose father is a teacher.（所有格）6. 關係代名詞的人稱、數、性必須和先行詞一致。
Ex：I, who am your friend, can understand you.You, who are my friend, can understand me.She, who is my good friend, is the best student in our class.The book which lies on the table is mine.The books which lie on th table are mine.P.S：one of+複數（代）名詞+關係代名詞+複數動詞Ex：He is one of those who were present.She is one of the few students who（＝that）have passed the examination.This is one of the good books which（＝that）are worth reading.◎who （主格）人+ whose （所有格）【＝關係形容詞】whom （受格）a.當主格時：This is the teacher + he teaches us English.＝This is the teacher who teaches us English.The people + they are there are my friends.＝The people who are there are my friends.That is the girl who speaks English.The children who played baseball were happy.b.當受格時：These are the students + he teaches them.＝These are the students （whom）he teaches.The foreigner + we met him is an American.＝The foreigner （whom）we met is an American.The man + I talked to him is a doctor.＝The man （whom）I talked to is a doctor.＝The man to whom I talked is a doctor.I know the man （whom）you visited.They were the men （whom）he was looking for.＝They were the men for whom he was looking.The men to whom I spoke are here.＝The men（whom）I spoke to are here.◎應注意事項1.除前面有介系詞的whom外，who與whom均可用that來代替。
2.用於限定用法（即形容詞子句）的受格關係代名詞whom與that可以省略。
但whom前面有介系詞時除外。
Ex：I know the man who visited you.＝I know the man that visited you.The mam（whom）we saw is Mr. Brown.＝The man（that）we saw is Mr. Brown.c.當所有格時：I have a friend + his sister is a teacher.＝I have a friend whose sister is a teacher.The girl + her work won the prize is here.＝The girl whose work won the prize is here.There was a man whose name was Rip.Here is the boy whose pen has been stolen.An orphan is a child whose parents are dead.which （主格）◎人以外的動物+ whose（of which）（所有格）或事、物which （受格）a.當主格時：I bought a book + it is very good.＝I bought a book which is very good.The cat + it caught a mouse is there.＝The cat which caught a mouse is there.Take the pencils which are on the table.He has a horse which runs very fast.The month which comes before May is April.b.當受格時：The books + I bought them yeaterday are nice.＝The books（which）I bought yesterday are nice.I like the house + he lives in it.＝I like the house（which）he lives in.＝I like the house in which he lives.This is the dog + I spoke of it.＝This is the dog（which）I spoke of.＝This is the dog of which I spoke.Here is the letter of which I told you.＝Here is the letter（which）I told you of.◎應注意事項1.which可用that來代替，但which前面有介系詞時除外。
2.用於限定用法的受格關係代名詞which可以省略，但which前面有介系詞時除外。
Ex：This is the horse which won the race.＝This is the horse that won the race.The book（which）he gave me is very good.＝The book（that）he gave me is very good.Is this the book of which you spoke?＝Is this the book（which）you spoke of?＝Is this the book（that）you spoke of?c.當所有格時：The book +its cover is green is mine.＝The book whose cover is green is mine.＝The book + the cover of it is green is mine.＝The book the cover of which is green is mine.＝The book of which the cover is green is mine.The mountain whose top we can see is Mt.Fuji.The book the cover of which is blue is Mary’s.＝The book of which the cover is blue is Mary’s.人◎動物+ that 【限於主格、受格；不可用作所有格】事物（＝who，whom，which）1.關係代名詞that可用以代替who，whom，which等，以代表人、動物、事物。
Ex：I want a man that（＝who）understands English.（主格）John is a boy that（＝whom）I like very much. （受格）2.先行詞前面有最高級形容詞時，須用that，不可用who或which。
Ex：This is the best book that I have ever read.He is the greatest inventor that ever lived.3.（the first，the last，the only，the same，the very，any，all，no）+先行詞+ thatEx：He is the first boy that came here. She was the last girl that arrived.She is the only girl that can ride a bicycle. Take any book that you like.This is the same man that came yesterday. This is all that I know about him.You are the very man that I wanted to see. I saw no one that I knew.4. 兩種先行詞（人+動物或事物）+ thatEx：Look at the boy and his dog that are crossing the bridge.The man and the horse that fell into the river were drowned.c.前面已有疑問詞who或which時，宜用that，以避免重複。