culture medium

Medium Me"di*um, 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]