The Collaborative International Dictionary of English v.0.48:
Medium \Me"di*um\, n.; pl. L. Media, E. Mediums. [L.
medium the middle, fr. medius middle. See Mid, and cf.
1. That which lies in the middle, or between other things;
intervening body or quantity. Hence, specifically:
(a) Middle place or degree; mean.
The just medium . . . lies between pride and
(b) (Math.) See Mean.
(c) (Logic) The mean or middle term of a syllogism; that
by which the extremes are brought into connection.
2. A substance through which an effect is transmitted from
one thing to another; as, air is the common medium of
sound. Hence: The condition upon which any event or action
occurs; necessary means of motion or action; that through
or by which anything is accomplished, conveyed, or carried
on; specifically, in animal magnetism, spiritualism, etc.,
a person through whom the action of another being is said
to be manifested and transmitted.
Whether any other liquors, being made mediums, cause
a diversity of sound from water, it may be tried.
I must bring together
All these extremes; and must remove all mediums.
3. An average. [R.]
A medium of six years of war, and six years of
4. A trade name for printing and writing paper of certain
sizes. See Paper.
5. (Paint.) The liquid vehicle with which dry colors are
ground and prepared for application.
6. (Microbiology) A source of nutrients in which a
microorganism is placed to permit its growth, cause it to
produce substances, or observe its activity under defined
conditions; also called culture medium or growth
medium. The medium is usually a solution of nutrients in
water, or a similar solution solidified with gelatin or
7. A means of transmission of news, advertising, or other
messages from an information source to the public, also
called a news medium, such as a newspaper or radio; used
mostly in the plural form, i. e. news media or media.
See 1st media.
Circulating medium, a current medium of exchange, whether
coin, bank notes, or government notes.
Ethereal medium (Physics), the ether.
Medium of exchange, that which is used for effecting an
exchange of commodities -- money or current
representatives of money.