1. a middle state or condition; mean.
2. something intermediate in nature or degree.
3. an intervening substance, as air, through which a force acts or an effect is produced.
4. the element that is the natural habitat of an organism.
5. surrounding objects, conditions, or influences; environment.
6. an intervening agency, means, or instrument by which something is conveyed or accomplished. "Words are a medium of expression".
7. one of the means or channels of general communication, information, or entertainment in society, as newspapers, radio, or television.

-Julie