Metaphor (noun)

1. A figure of speech in which a word or phrase is applied to an object or action to which it is not literally applicable.
2. Something used, or regarded as being used, to represent something else; a symbol.

Origin:

Late latin metaphora, from greek metaphora 'a transfer', from metapherein 'to transfer', from meta- 'over, across' + pherein 'to bear, carry'.

Examples:

1. The teacher used the metaphor of a journey to describe life.
2. The heart of a city is a common metaphor for its central area.
3. She was a rose, a metaphor for her delicate beauty.
4. The metaphor of the sun and moon to describe the relationship between two people is ancient.
5. The metaphor of a web to describe the interconnectedness of things is a familiar one.