*medium*

n.; pl. L. Media E. Mediums [ L. medium the middle, fr. medius middle. See Mid, and cf. Medius. ] 1. That which lies in the middle, or between other things; intervening body or quantity. Hence, specifically: (a) Middle place or degree; mean. [ 1913 Webster ]

The just medium . . . lies between pride and abjection. L'Estrange. [ 1913 Webster ]

(b) (Math.) See Mean. (c) (Logic) The mean or middle term of a syllogism; that by which the extremes are brought into connection. [ 1913 Webster ]

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. [ 1913 Webster ]

Whether any other liquors, being made mediums, cause a diversity of sound from water, it may be tried. Bacon. [ 1913 Webster ]

I must bring together
All these extremes; and must remove all mediums. Denham. [ 1913 Webster ]

3. An average. [ R. ] [ 1913 Webster ]

A medium of six years of war, and six years of peace. Burke. [ 1913 Webster ]

4. A trade name for printing and writing paper of certain sizes. See Paper. [ 1913 Webster ]

5. (Paint.) The liquid vehicle with which dry colors are ground and prepared for application. [ 1913 Webster ]

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 agar. [ PJC ]

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{ 2 }. [ PJC ]

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. [ 1913 Webster ]

a. Having a middle position or degree; mean; intermediate; medial; as, a horse of medium size; a decoction of medium strength. [ 1913 Webster ]