A relative pronoun can be used to introduce to two types of clauses called restrictive and non-restrictive relative clauses. 

 

Restrictive / defining relative clause

A restrictive relative clause (also called a defining relative clause) gives information about the noun which can be someone or something in the main clause. The restrictive clause usually comes after the noun, and it cannot be removed from the sentence without affecting its meaning. The word that is used much more frequently than other relative pronouns such as whowhom and which in a restrictive clause. By using that, it makes the clause essential to the meaning of the sentence. Commas are not used in restrictive clauses. Whose may also be used. 

 

A restrictive relative clause (also called a defining relative clause) is essential to the meaning of the sentence.  It gives information about the noun which can be someone or something in the main clause. It usually comes after the noun.  The defining relative clause cannot be removed from the sentence without affecting its meaning. The word that is used much more frequently than whowhom or which in a defining relative clause. Whose may also be used in both types of clauses. Commas are not used in defining relative clauses.

 

The information given by a restrictive relative clause helps to identify the noun that is being referred to. The following examples show the restrictive clauses in bold.

 

Examples:

  • That is the ship which is said to be haunted..
  • Police found the woman that owns the place.
  • The boy who is pointing at the sky saw a UFO.

 

The relative pronouns used above (whichthatwho) act as subjects. Each of them introduces a restrictive clause that defines or identifies the noun/subject which precedes it. If a restrictive clause is removed, the noun (house, man, woman) is no longer identified and as a result, the sentence does not make sense or in some cases, it gives a different meaning. 

 

Examples:

  • That is the ship. (What is it about the ship?)
  • Police found the woman. (What about the woman?)
  • The boy saw a UFO. (Which boy saw the UFO?)

 

 

In restrictive clauses, that can be used to replace who, whom, or which 

Examples:

  • It was a young couple who moved in next door.
  • It was a young couple that moved in next door.
  • It was her parents whom he was most anxious to meet.
  • It was her parents that he was most anxious to meet.
  • The coconut which dropped on his left ear nearly killed him.
  • The coconut that dropped on his left ear nearly killed him. 

 

 

A relative pronoun can define the subject of the verb in a restrictive clause. When the relative pronoun is the subject, it cannot be omitted from the sentence. Using the restrictive clauses, the following show the omission of the relative pronouns.

Examples:

  • Incorrect: I think I know that woman walked onto the stage.
    Correct: I think I know that woman who walked onto the stage. 
  • Incorrect: This is the old house is without a roof.
    Correct: This is the old house which is without a roof.  
  • Incorrect: He was the man killed the crocodile.
    Correct: He was the man that killed the crocodile. 

 

 

A relative pronoun can define an object of the verb in a restrictive clause. The relative pronoun which is an object can be omitted.

Examples:

  • The repairman whom you called has arrived.
  • The repairman you called has arrived.
  • The fish that you caught will be cooked for dinner..
  • The fish you caught will be cooked for dinner.

 

 

Whenwherewhose and why can be used in restrictive relative clauses.

Examples:

  • I regret passing up those opportunities when I could have got married.
  • That is the bullring where we used to watch bullfights.
  • That is my fat auntie whose husband is a lot fatter than her.
  • There are a few reasons why I can’t lend you the money.

 

 

 

Non-restrictive / non-defining relative clause

A non-restrictive relative clause (also called non-defining clause) adds extra information about a noun which already has a clear reference. The information is not necessary so that if a non-restrictive clause is removed from the sentence, the sentence will still make sense. The relative pronoun that is not used in a non-restrictive clause; instead, whowhomwhose or which is used to introduce the non-restrictive clause.

 

A comma is used before a non-restrictive clause. If the non-restrictive clause is in the middle of a sentence, it is enclosed by commas.

 

Examples:

  • Nick, who is my good friend, has made it to the final of the competition.
  • My cousin Dick, whose father is my father’s elder brother, and I have been good mates ever since we were at school together.  

 

 

That is not used for a non-restrictive clause.  

Examples:

  • No: His grandfather is Mr Beardson that has a long beard. 
  • Yes: His grandfather is Mr Beardson, who has a long beard. 
  • No: He collects peacock feathers that he started five years ago. 
  • Yes: He collects peacock feathers, which he started five years ago. 
  • No: The dog that we bought recently is always barking loudly at cats.
  • Yes: The dog, which we bought recently, is always barking loudly at cats.

 

 

The following examples show that the relative pronouns who and which are used as the subjects of non-restrictive clauses, and that the sentences still make sense with the removal of the non-restrictive relative clauses.

 

Examples:

  • The Mona Lisa was painted by Leonardo da Vinci, who was also a prolific engineer and inventor.
  • The Mona Lisa was painted by Leonardo da Vinci.
    (The relative clause who was also a prolific engineer and inventor is a non-restrictive clause that is added to the main clause just give more information. Its removal does not affect the grammar of the sentence.)
  • Sam, who died last year, was our favourite uncle.
  • Sam was our favourite uncle. (The past tense verb was shows Sam is no longer living.)
  • She often walks to the library, which is not far from her house.
  • She often walks to the library.

 

 

The relative pronouns whowhom and which may be used as objects in non-restrictive clauses.

Examples:

  • One of our classmates is Alice, who we like.
    (Who is usually used as the subject, but sometimes it is used as an object in place of whom.)
  • His girlfriend ran away with his best friend, whom he trusted.
  • He is selling his wheelbarrow, which is a big one.

 

 

A non-restrictive clause may be used to describe the whole main clause.

Examples:

  • He left to work overseas, which was a great loss to us.
  • We have not had a car for a few years, which means that we have saved a lot on fuel and maintenance.

 

 

Difference between restrictive/defining and non-restrictive/non-defining clauses.

Examples:

  • Bobby's sister, who works as a nurse, is my sister's friend.
    (Bobby has only one sister who is a nurse.)
  • Bobby's sister who works as a nurse is my sister's friend. 
    (Bobby has more than one sister, and the one who is my sister's friend is a nurse.)