Writing Skills

A relative clause is a subordinate clause that modifies a noun or a nominal.

Defining relative clauses give essential information about the noun. When the noun modified is a person and also a subject of that clause, who is usually used.

• CORRECT: The woman who won the race was given a first place trophy.

That can be used instead of who after all, everyone, everybody, no one, nobody, those:

• CORRECT: Everyone that attended the concert was given a free keychain.

When the noun modified is a person and also an object, who, that, or whom may be used. Or the relative pronoun may be omitted.

• CORRECT: The mechanics whom this shop employs come from a wide range of backgrounds. 
• CORRECT: The mechanics who this shop employs come from a wide range of backgrounds.  
• CORRECT:  The mechanics that this shop employs come from a wide range of backgrounds. 
• CORRECT:  The mechanics this shop employs come from a wide range of backgrounds. 

With prepositions we can use either whom or that. The use of whom is more formal.

• CORRECT: The man with whom I took this class has already gone home.
• CORRECT: The man that I took this class with has already gone home.

When the noun modified is a thing and a subject of that clause, which or that can be used. The use of which is more formal.

• CORRECT: This is the moment that I have been waiting for.
• CORRECT: This is the moment which I have been waiting for.

If the relative clause modifies an object of a verb, which, that, or no relative pronoun can be used. Which is rarely used after all, everything, little, much, none, no, or after superlatives.

• CORRECT: The book which I bought this morning was missing.
• CORRECT: This is the best movie I have ever seen.

To express possessive, only one form is possible: whose.

• CORRECT: The woman whose car had broken down was later picked up by a friend.

Non-defining relative clauses provide non-essential or extra information about the noun or the nominal. Unlike defining relative clauses, non-defining relative clauses are separated from the noun by commas. The pronoun cannot be omitted in a non-defining relative clause.

When the noun modified is a person and a subject of the clause, only the relative pronoun who can be used in non-defining relative clauses.

• CORRECT: Scott, who is an excellent dancer, was invited to teach lessons at the community center.

When the noun modified is a person and also an object of the clause, whom is used. 

• INCORRECT: Gretchen, that everyone loves, is known for her wit and fun personality. 
• CORRECT: Gretchen, whom everyone loves, is known for her wit and fun personality. 

When the modified noun is an object of a preposition, whom is used.

• CORRECT: Charles, with whom I had only just met, was eager to share stories of his childhood.

Possessive is expressed by whose.

• CORRECT: Beth, whose poetry skills were widely regarded, was invited to perform at the conference. 

In non-defining relative clauses, we mostly use which to modify nouns that are either subjects, objects, or objects of a preposition.

• CORRECT: The graphics card, which I had just installed, was causing an error.  

Connective relative clauses (one of ..., two of ..., several of ...) do not define nouns, but rather continue the story. Whom is used with persons and which with things.

• CORRECT: There were several positions available at the company, one of which required a Masters degree.
• CORRECT: I met the governing board, one of whom advised me on today's minutes.  

Whoever and whichever can mean "the one who" or "no matter who."

• CORRECT: This position will be given to whoever scores best on the practical portion of the interview.
• CORRECT: This position is for whomever we choose to be the best candidate.