A relative clause tells more information about the noun it relates to. It describes and identifies the noun.
We begin a relative clause with a relative pronoun. Relative pronouns are :
who, whom, which, that, whose, where.
who, whom : for people
where : for places
which : for animals and things
whose : for possession
In informal speech "who" is used for people and things.
*** I know a man. He can speak three languages very well.
*** I know a man who can speak three languages very well.
*** My mother met a woman. She owns a hotel.
*** My mother met a woman who owns a hotel.
*** My dog is very clever. I bought it a year ago.
*** My dog which I bought a year ago is very clever.
*** Jack works for a company. It produces cars.
*** Jack works for a company which produces cars.
*** A tailor is a person. He sews clothes and dresses.
*** A tailor is a person who sews clothes and dresses.
*** Antalya is a wonderful city. You can visit a lot of historical places there.
*** Antalya is a wonderful city where you can visit a lot of historical places.
*** Ayse is a teacher. I met her in Manisa.
*** Ayse, who I met in Manisa, is a teacher.
*** Mr. Brown is an old man. His son lives in Japan.
*** Mr. Brown; whose son lives in Japan, is an old man. / Mr. Brown is an old man whose son lives in Japan
Defining Relative Clauses :
Defining Relative Clauses identify nouns, and tell us which person or thing the speaker refers to. It gives essential information, so we don't use commas to separate it from the rest of the sentence.
*** The house which we bought is very large, (defining Relative Cl. tells us which house)
*** I met a girl who lived in an orphanage for fifteen years, (defining relative Cl. Tells us which girl)
*** The people who have much experience in this job will be employed, (defining relative Cl. tells us which people)
*** The factory where my father works will close down. (defining relative Cl. tells us which factory)
*** The manager whose son died in a traffic accident is very helpful and friendly. (defining relative cl. tells us which manager)
We can use who, that, and which for subject or the object of a defining relative clause. If we use them for the object of the clause, we can omit the relative pronouns.
See the difference;
*** I bought a book. It is very interesting
*** I bought a book which is very interesting, (we cannot omit which, it refers to the subject of the clause)
*** Mary is the girl. She invited us to her house.
*** Mary is the girl who invited us to her house, (we cannot omit who, it refers to subject of the clause)
*** I spoke to the woman. She has ten children.
*** I spoke to the woman that has ten children, (we cannot omit that, it refers to subject of the clause.)
*** Mary is the girl. I met her at a party.
*** Mary is the girl (who) I met at a party, (we can omit who, because it is used for the object of the clause)
*** The necklace is very valuable. My grandmother gave me it.
*** The necklace (which) my grandmother gave me is very valuable, (we can omit which because it is used for the object of the clause)
Non-Defining Relative Clause :
Non-defining Relative Clauses don't tell us which person or thing the speaker is talking about. They give us extra information about the person or a thing that has already been identified. We use commas to separate the clauses from the rest of the sentence.
*** My father, who is retired, doesn 't like sitting without doing anything, (non-defining relative clause gives us extra information)
*** The students, who are eager to learn, do all the exercises very well.
*** My father gave me the photographs, which I put on my table.
*** My friends liked my dress, which my mother had made for me.
*** Mr. and Mrs. ^imsek, who are our neighbours, went to Kayseri.
In non-defining relative clauses, we cannot omit the relative pronouns. And also we cannot use "that" in non-defining relative clauses.
*** The bicycle, which I bought last month, broke down. (not that, but which)
*** Mike, whose parents are in the USA, has lived in Izmir for two years.
*** Last weekend we went to Karagol, where we had a picnic.
*** Some of my friends, who I had invited to my party, weren 't able to come.
*** Whom refers to people and it is used with a preposition.
*** Emre is one of my students. I gave a book to him.
*** Emre , to whom I gave a book, is one of my students.
*** Emre, who I gave a book to, is one of my students.
*** Ceren is a girl. I spend most of my time with her.
*** Ceren is the girl, with whom I spend most of my time.
*** Ceren is the girl, who I spend most of my time with.