Sentences can also be combined by the use of Adjective Clauses to describe or qualify or enlarge a noun or pronoun. In such sentences there are two clauses, the main clause and the adjective clause.

He has a dog which cost him two hundred rupees.

Here He has a dog is the main clause, and the rest of the sentence is the adjective clause.

Such adjective clauses are introduced by who, whose, whom, which, or that. With whom and which various prepositions can be used, such as to whom, by which, etc.

That is the lady. She married a famous Spaniard.
That is the lady who married a famous Spaniard.

I saw a dwarf at Kakawewa station. He was only two feet high.
At Kalaveva station I saw a dwarf who was only two feet high.

That is the boy I spoke of. His cousin is a well-known poet.
That is the boy I spoke of, whose cousin is a well-known poet.

Here lives a rich old gentleman. I was speaking to you about him only yesterday.
Here lives the rich old gentleman of whom I was speaking to you only yesterday.

This is my friend. I received a beautiful watch from him recently.
This is my friend from whom I received a beautiful watch recently.

Here comes Mr. Herath. I learnt Sanskrit from him.
Here comes Mr. Herath, from whom I learnt Sanskrit.

Take him to Dr. Harischandra. He lives just round the corner.
Take him to Dr. Hariscandra who lives just round the corner.

See if you can find my spectacles. I left them in the library.
See if you can find my spectacles, which I left in the library.

Where is the lock of this drawer? This key belongs to it.
Where is the lock of this drawer to which this key belongs?

Have you seen the red dictionary? I put it on this table yesterday.
Have you seen the red dictionary that I put on this table yesterday?

This is the new theatre. It was damaged by fire last month.
This is the new theatre that was damaged by fire last month.

Note: In sentences like these, which may be used for that. But more frequently neither is used. We say:

Have you seen the dictionary I put on the table yesterday?
This is the book I bought at the railway bookstall.