Medium

A substance used to provide nutrients for cell growth. It may be liquid (e.g., broth) or solid (e.g., agar).

Pertaining to the middle.

The substance or material in which anything moves or acts.

Average, in the middle or at the halfway point.

Substance through which something moves or acts. A contrast medium, for example, has a density different from body tissues and when used with X ray or similar technique allows visual comparison of structures.

Any substance, usually a broth, agar, or gelatin, used for the culture of microorganisms or tissue cells. An assay medium is used to determine the concentration of a growth factor or chemical by measuring the amount of growth it produces in a particular microorganism; all other nutrients are present in amounts adequate for growth.

In the context of pseudoscience, an intermediate agency in the world of spiritualism a person who mediates between the spirit world and the material world. Mediums perform at a seance or sitting, where they enter into a trance a halfway state between sleeping and waking from where they claim they can connect with the dead (or in their words “those who have passed over”) and transmit their messages to living relatives or loved ones here on Earth.