What does "medium" mean?

Medium: 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. Bacon. I must bring together All these extremes; and must remove all mediums. Denham.

Additional senses

  1. 2.An average. [R.] A medium of six years of war, and six years of peace. Burke.
  2. 3.A trade name for printing and writing paper of certain sizes. See Paper.
  3. 4.(Paint.) The liquid vehicle with which dry colors are ground and prepared for application. 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.
  4. 5.Having a middle position or degree; mean; intermediate; medial; as, a horse of medium size; a decoction of medium strength.

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