I was asked a good question on Twitter yesterday by @Risachan7:

"This is his city, which he left ten years ago.のwhichってなんでwhereじゃないんですか？

If you don't read Japanese this is the question:

In this sentence, "This is his city, which he left ten years ago", why does it say "which" and not "where"?

Remember that we use a joining word to connect a noun to the adjective phrase:

1. "the place where James was born";
2. "the people that we met on vacation";
3. "the souvenirs which Ben and Claire bought".

These joining words can be left out. We sometimes cut the joining words in spoken English and in informal writing:

1. "the place James was born";
2. "the people we met on vacation";
3. "the souvenirs Ben and Claire bought".

This is not always possible.

There are two main types* of adjective clause:

1. a "describing clause"—a clause that tells us more about something or someone;
2. an "identifying clause"—a clause that identifies something or someone.

These two types of clause are different in some ways:

• They are said differently;
• They use different punctuation;
• They mean something different.

An adjective clause (sometimes called a relative clause) is a phrase that is used to give more information about a noun. Look at this example:

That is the place where James was born.

This sentence is about a place. It uses the phrase "where I was born" to say which place.

Here are some more examples:

He's the man who lives next door.
This is the house where she lived.
These are the souvenirs which Ben and Claire bought in Turkey.