Relative clauses give more information about a subject or object.

They usually follow and “agree” with the noun they modify and often occur between a Subject and Verb. 

However, they usually have no effect on the S + V relationship.

• The man who works at IBM comes from Hong Kong.
• The house that Jack built remains empty.
• The people who came to the party had a great time.
• Those who arrive early are entitled to a rebate.
• I ate an apple that had a worm in it.
• She is the one who I told you about.
• The man who lives over there is my uncle.
• One of the men who lives over there is my uncle.
• Only one of the people who work in the company is qualified.

Most relative clauses use the words who, whom, whose, which, that, when or where.

• This is the place where I met my wife.

Commas which set off relative clauses function like parentheses ( ) indicating non-essential information.

• • My wife, who is a doctor, works at Community Hospital.
  • My wife (who is a doctor) works at Community Hospital.

Without commas, relative clauses specify one member of a group:

• • My brother who is a scientist works at the university.
  • My brother who is a mechanic works at Bob’s Garage.

Specifies “which brother” (one of many)