Possible Definitions:
1. Medium (n.) That which lies in the middle, or between other things; intervening body or quantity. Hence, specifically: (a) Middle place or degree; mean.
2. Medium (n.) See Mean.
3. Medium (n.) The mean or middle term of a syllogism; that by which the extremes are brought into connection.
4. Medium (n.) 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.
5. Medium (n.) An average.
6. Medium (n.) A trade name for printing and writing paper of certain sizes. See Paper.
7. Medium (n.) The liquid vehicle with which dry colors are ground and prepared for application.
8. Medium (a.) Having a middle position or degree; mean; intermediate; medial; as, a horse of medium size; a decoction of medium strength.
