Medium

The word medium has a number of uses:

• The most common meaninf of the word medium is an average or mean in a range of sizes or conditions. Usually, the term is used when there are only a few different sizes in the range, rather than many. For example, items such as drinks at a fast food restaurant might come in three sizes: Small, Medium, and Large.
• When relating to the bearing of something, a medium (bearer) (plural media) is a process or object that can carry, transmit, or store something.
• A medium (spirituality) is an individual who claims the ability to receive or channel messages from spirits, ghosts, or other discorporate entities.
• In microbiology and other scientific disciplines, a medium is a nutrient system for the artificial cultivation of cells or organisms and especially bacteria.
• In communications, an intervening substance through which a message or information is transmitted or carried on.
• In art, a specific kind of artistic technique or means of expression or the materials used in a specific artistic technique.
• A medium (optics) is something that is homogeneous on lengthscales comparable with the wavelength of the light being considered.

The word medium comes directly from Latin, in which it means, "the one in the middle."

The plural, "mediums" is sometimes used. The plural, "media" is not to be confused with the technical term, "media", which pluralizes to "mediae".

Interestingly, the peculiarities of the English language and its use of the same word for different meanings allow English speakers to make such statements as, "Small medium at large!" that are both comprehensible and mildly amusing.