An adjective clause or a relative clause is a dependent clause introduced by a relative pronoun or relative adverb. It functions as an adjective; that is, it modifies or describes a noun or pronoun in the independent clause.
1) Relative Pronouns: A relative pronoun replaces a noun phrase or pronoun in the dependent clause. The relative pronouns are:
| Subordinator | Meaning |
| Who | Refer only to people and is a subject pronoun |
| Whom | Refers only to people and is an object pronoun. |
| Which | Refers to things or animals and is a subject or object pronoun. |
| That | Refers to things, animals or people and is a subject or object pronoun in restrictive or defining clause only. |
| Whose + noun | Refers to things, animals or people and is a possessive. |
Example:
- Students who like study usually try hard to do research.
- Mr. Phearum married Ms Kanhchana whom I know very well.
- The car which I want to buy is available in Kampong Speu.
- These are the candidates that will compete on Christmas Day.
- I know the poor man whose son was killed last week.
2) Relative Adverbs: A relative adverb replaces a prepositional phrase in the dependent clause. The relative adverbs are:
| Subordinator | Meaning |
| Where When Why | Refers to a place. Refers to a time. Refers to a reason. |
Example:
- I want to visit Angkor Wat where most of the tourists want to see.
- We will never forget the time when we share happiness and sadness together.
- Mr. Kheang didn’t tell me the reason why he gave up his study.
Relative Pronouns as Object of Prepositions formed in two ways:
| Pronoun + whom/which/(whose + noun) + subject + verb + complement (formal) |
| Whom/which/(whose + noun) + subject + verb + complement + Preposition (informal) |
Example:
- The candidate for whom I voted didn’t win the election. (formal)
- The candidate whom I voted for didn’t win the election. (informal)
