Definition of "monad" [mon•ad]

• Philosophy An indivisible, impenetrable unit of substance viewed as the basic constituent element of physical reality in the metaphysics of Leibniz. (noun)
• Biology A single-celled microorganism, especially a flagellate protozoan of the genus Monas. (noun)
• Chemistry An atom or a radical with valence 1. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The term monad is, however, generally understood in reference to the philosophy of"
• "Since Leibniz 'time the term monad has been used by various philosophers to designate indivisible centres of force, but as a general rule these units are not understood to possess the power of representation or perception, which is the distinguishing characteristic of the Leibnizian monad."
• "Note 127: "According to Capella," Pérez-Gómez notes, "the monad is all that is good, desirable and essential — a notion that was explicitly introduced into Renaissance theology by Nicholas of Cusa in his influential work De docta ignorantia.""