Adjective clauses are used to describe things, people and places. They are a phrase that comes after a noun. They tell us more about that noun. For example:

"the person who lives next door"; or
"the time that we went to Disneyland".

Remember that an adjective clause needs three things:

1. a noun (the thing you are describing);
2. a joining word (relative pronoun or relative adverb);
3. a clause with:
   1. a subject, and
   2. a verb.

Here are some examples:

• the place where James was born
• the souvenirs which  Ben and Claire bought
• the people that we met 
• he day when the couple went on their first date

To review, read the introduction to adjective clauses.

Types of adjective clause

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.

1. Describing clauses

We use a describing clause to give more information about something or someone. That something or someone is already known. It is something or someone that has already been introduced or talked about. The information in the describing clause is a bonus. It is not needed in the sentence, but it is nice when we can add something.

Take a look at these examples and pay special attention to the adjective clauses:

1. Naoto, who works for a Swiss company, studied English in Australia.
2. Naoto likes to watch True Blood, which is a show about vampires.

Our sentences do not need this information. Look at them without the adjective clauses:

• Naoto studied English in Australia.
• Naoto likes to watch True Blood.

Both these sentences are fine without the adjective clauses. We know less about Naoto in sentence one, and we maybe don't know what "True Blood" is in sentence two, but these sentences are still OK.

We need to show that the clause is not super important to the sentence. We do this with commas when we write and pauses when we speak. You must split it from the sentence with commas (when you write) or a pause (when you speak). Take another look at our two examples:

1. Naoto, who works for a Swiss company, studied English in Australia.
2. Naoto likes to watch True Blood, which is a show about vampires.

When you write, you need to use commas before and after a describing adjective clause that comes in the middle of your sentence (like sentence one). In sentence two, when the clause comes at the end, you don't need a comma after because there is a period.

When you speak, these punctuation marks show little pauses. Read these two sentences out loud, with pauses where you see the //.

1. Naoto//who works for a Swiss company//studied English in Australia.
2. Naoto likes to watch True Blood//which is a show about vampires.

Sentence one has three parts and sentence two has two parts. Your intonation should show this. If you are not sure, ask your teacher or a native speaker to read these sentences for you.

Both of our example sentences include adjective clauses which describe the noun before them. In sentence one, that noun, "Naoto", is a guy we might or might not know, but he is identified by his name. It would be strange to say something like this:

• "A man, who works for a Swiss company, studied English in Australia,"

because we don't know who that man is. The information in the adjective clause does not identify the man.

2. Identifying clauses

An identifying clause tells us exactly which person or thing, or which type of person or thing. It limits what we are talking about. We can use this kind of adjective clause to talk about a specific person, or thing (or a type of person or thing). These adjective clauses identify things and people:

1. People who are good at music are good at languages.
2. What is the name of the TV show that you like?

In these kinds of sentences, the adjective clause is very important. Look what happens when we take the adjective clause out:

1. People are good at languages. 
2. What is the name of the TV show?

These sentences communicate much less because they are not clear. Sentence one is silly now. Saying "People are good at languages" is like saying "Fish are good at swimming". It's not a very meaningful sentence. Sentence two only makes sense if you know which TV show.

Let's try it the other way. How are these sentences?

1. Fish are called "flying fish".
2. Animals eat meat.

There is something wrong with these two sentences. Fish are called "fish", but some kinds of fish are called "flying fish". The person who says sentence two has never met a rabbit, a sheep or a vegetarian. There are lots of animals that do not eat meat. How about if we add something to our sentence to identify the things we are talking about?

1. Fish that fly are called "flying fish".
2. Animals which have sharp teeth and claws eat meat. 

It is easy to see that you need an identifying clause in your sentence. It gives a little extra information to limit our sentence. By limiting our sentence, we can say something that makes sense.

The information in the identifying clause is important, so we don't use commas or pauses to separate it from the main sentence.  Actually, the whole phrase of noun and adjective clause becomes a noun phrase (that is used as part of the sentence). The examples really are more like this (in an English speaker's brain):

1. People who are good at music are good at languages. 
2. What is the name of the TV show that you like?
3. Fish that fly are called "flying fish".
4. Animals which have sharp teeth and claws eat meat.

When you read these sentences out loud, there should be no pauses. Ask a native speaker or your teacher to help you if you are not sure.

When to use "that"

If you read the article on adjective clauses, you know "that" can be used in place of "who", "when", "where", "which" and "why". However, now that you know about identifying and describing relative clauses, you can learn a little bit more about "that".

When you use an identifying clause, you can use "that". Here are some examples:

However, when you use a describing clause, you cannot use "that".