Medium

In art, two meanings:

1. The material in which an artist works: paint, ink, wood, marble, steel, etc.
2. In paint, the liquid in which the pigment is suspended. Pigment in its usual state is a dry substance. Medium allows the pigment to be spread and to adhere to the painted surface. Water, gums, waxes, oils, and egg are common media.

In science:

1. A carrier. E.g., when salt is soluted in water then water is the medium.
2. Political media. Press, TV, internet

In religion:

1. A person who acts as a 'mediator' between the living and the dead spirits.