The dress, which you can get at any shop, is popular this spring.

The dress which you want can be found at any shop.

　　In the first sentence, the clause ' which you can get at any shop' gives extra information.

It tells you where you can get the dress.

In the second sentence, the clause tells us that the dress is just what you want, not anyone else.

She introduced me to her husband, whom I hadn't met before.

She introduced me to the man who is her husband.

In the first sentence, we can know who she introduced. The clause just tells us that this was the

first time I met her husband.

In the second sentence, the clause tells us who the man is.

His sister, who is studying in England, will be back this summer.

His sister who is studying in England will be back this summer.

The first sentence tells us that he has a sister and she is now studying in England and will be

back this summer, while the second sentence tells us that maybe he has more than one sister and one

of them is now studying in England and will be back this summer.

The books, in which there are beautiful pictures, are for children.

The books in which there are beautiful pictures are for children.

In the first sentence, we know the books are all for children and they have beautiful pictures in

them. In the second sentence, we know only the books with beautiful pictures are for children, while

the books without beautiful pictures are not for children. 5. More examples

1) All the magazines here which have beautiful pictures in them were written by him.

2) All the magazines here, which have beautiful pictures in them, were written by him.

3) This is the place where I lived ten years ago.

4) She is going to spend the winter holiday in Macao, which returned to China in 1999.