Traditionally，metaphor is a figure of speech in which one thing is compared to another by saying that one is the other，as in“He is a tiger”. It is a property of words，and is used for some artistic and rhetorical purpose. However，this view has been challenged recently by cognitive linguists. In the cognitive linguistic view，metaphor is a property of concepts，and it is a powerful cognitive tool for our conceptualization of abstract categories. It is pervasive in our language.

According to cognitive linguistics，metaphor is defined as understanding one conceptual domain or cognitive domain in terms of another conceptual domain. The conceptual domain from which we draw metaphorical expressions to understand another conceptual domain is called source domain (“tiger”in the above example)，while the conceptual domain that is understood this way is called target domain (“He” in the above example). Thus，metaphor can be diagrammed as follows：

CONCETUAL DOMAIN (A) IS CONCEPTUAL DOMAIN (B)

 

  

TARGET DOMAIN   SOURCE DOMAIN

He                      is         a    tiger

Thus，in cognitive linguistics metaphor is called conceptual metaphor because it is a property of concepts. From this diagram we can see that a conceptual metaphor consists of two conceptual domains，in which one domain is understood in terms of another. Some examples of conceptual metaphor are in the following：

（1）LOVE IS A JOURNEY

Look how far we've come.

Well just have to go our separate ways.

We can't turn back now.

Our marriage is on the rocks.

We've gotten off the track.

This relationship is foundering.

（2）IDEAS ARE FOOD

There are too many facts here for me to digest them all.

I just can't swa/tow that claim.

Thafs food for thought.

He devoured the book.

（3）AN ARGUMENT IS WAR

Your claims are indefensible.

They attacked every weak point in our argument.

I’ve never won an argument with him.

You disagree? Okay，shoot！

If you use that strategy，he'll wipe you out.

He shot down all of my arguments.