We have already seen that an adjective clause is a subordinate clause that does the work of an adjective. It qualifies a noun or pronoun in the main clause.
An adjective clause is introduced by a relative pronoun or a relative adverb.
- Uneasy lies the head that wears the crown. (Here the adjective clause is introduced by the relative pronoun that.)
- The reason why she did it is obvious. (Here the adjective clause is introduced by the relative adverb why.)
- The site where the accident occurred is nearby.
- He is the boy who won the first prize.
The relative pronoun or relative adverb introducing an adjective clause is sometimes understood, and not expressed.
- Eat all that you can. OR Eat all you can.
- I saw a man whom I knew. OR I saw a man I knew.
- Where is the parcel that he sent to me? OR Where is the parcel he sent to me?
- The reason why I have come is to ask for my money. OR The reason I have come is to ask for my money.
A to-infinitive can often replace an adjective clause.
- Give me some water which I can drink.
- Give me some water to drink.
- He has no clothes which he can wear.
- He has no clothes to wear.
- I have some work which I must do.
- I have some work to do.