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monad

[mon-ad, moh-nad]
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noun
  1. Biology.
    1. any simple, single-celled organism.
    2. any of various small, flagellate, colorless ameboids with one to three flagella, especially of the genus Monas.
  2. Chemistry. an element, atom, or group having a valence of one.Compare dyad(def 3), triad(def 2a).
  3. Philosophy.
    1. (in the metaphysics of Leibniz) an unextended, indivisible, and indestructible entity that is the basic or ultimate constituent of the universe and a microcosm of it.
    2. (in the philosophy of Giordano Bruno) a basic and irreducible metaphysical unit that is spatially and psychically individuated.
    3. any basic metaphysical entity, especially having an autonomous life.
  4. a single unit or entity.
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Origin of monad

1605–15; < Late Latin monad- (stem of monas) < Greek (stem of monás): unity. See mon-, -ad1
Related formsmo·nad·ic [muh-nad-ik] /məˈnæd ɪk/, mo·nad·i·cal, mo·nad·al, adjectivemo·nad·i·cal·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for monadal

monad

noun
  1. plural -ads or -ades (-əˌdiːz) philosophy
    1. any fundamental singular metaphysical entity, esp if autonomous
    2. (in the metaphysics of Leibnitz) a simple indestructible nonspatial element regarded as the unit of which reality consists
    3. (in the pantheistic philosophy of Giordano Bruno) a fundamental metaphysical unit that is spatially extended and psychically aware
  2. a single-celled organism, esp a flagellate protozoan
  3. an atom, ion, or radical with a valency of one
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Also called (for senses 1, 2): monas
Derived Formsmonadical, adjectivemonadically, adverb

Word Origin

C17: from Late Latin monas, from Greek: unit, from monos alone
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for monadal

monad

n.

"unity, arithmetical unit," 1610s, from Late Latin monas (genitive monadis), from Greek monas "unit," from monos "alone" (see mono-). In Leibnitz's philosophy, "an ultimate unit of being" (1748). Related: Monadic.

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Online Etymology Dictionary, © 2010 Douglas Harper

monadal in Medicine

monad

(mōnăd′)
n.
  1. An atom or a radical with a valence of 1.
  2. A single-celled microorganism, especially a protozoan of the genus Monas.
  3. Any of the four chromatids of a tetrad that, after the first and second meiotic divisions, separate to become the chromosomal material in each of the four daughter cells.
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Related formsmo•nadic (mə-nădik) null adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.