Terms used to discuss adjective clauses:
adjective clause = relative clause
essential clause = defining clause = identifying clause
non-essential clause = non-defining clause = non-identifying clause
(1) An adjective clause is used to describe a noun. It follows the noun that it describes.
- The car that is parked outside belongs to Young-Hee.
(2) A relative pronoun is usually used to introduce a relative clause:
- Young-Hee, who is a Korean student, lives in Hayward.
(3) The main relative pronouns are:
Who: used for humans in subject position:
- Hans, who is an architect, lives in Berlin.
Whom: used for humans in object position:
- Marike, whom Hans knows well, is an interior decorator.
Which: used for things and animals in subject or object position:
- Marike has a dog which follows everywhere.
That: used for humans, animals and things, in subject or object position:
- Marike is decorating a house that Hans designed.
(4) There are two kinds of adjective clauses:
Non-defining (or non-essential) clauses give extra information about the noun, but are not essential:
- The desk in the corner, which is covered in books, is mine.
(We don’t need this information to understand the sentence. “The desk in the corner is mine” is a good sentence on its own–we still know which desk is referred to. Note that a non-defining clause is separated by clauses, and the relative pronoun that is not used in a non-defining clause.)
Defining (or essential) clauses give essential information about the noun:
- The package that arrived this morning is on the desk.
(We need this information in order to understand the sentence. Without the relative clause, we don’t know which package is being referred to. Note that that is often used in defining relative clauses, and they are not separated by commas.
(5) Another way to think about defining and non-defining clauses:
The defining adjective clause defines a sub-group.
- The students who missed the test yesterday need to talk to the teacher.
(There are many students, but only a small group of them missed the test. These are the students who need to talk to the teacher.)
The non-defining adjective clause simply gives more information about the noun it describes. It gives information about the same noun that it modifies:
- International students, who pay high tuition, often want to skip levels in the program.
(International students the students who pay high tuition are the same group of students.)