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From Ancient Greek δυάς (dyás), δυάδ- (dyád-) from Ancient Greek δύο (dýo) from Ancient Greek δύο (dúo), from Proto-Indo-European *duwó,*duwéh₃ (*dwóh₁). “dyad” in The American Heritage Dictionary of the English Language, 4th edition, Boston, Mass.: Houghton Mifflin, 2000, →ISBN.


dyad (plural dyads)

  1. A set of two elements treated as one; a pair.
    • 1908, W. D. Ross, Metaphysics, translation of original by Aristotle:
      ... positing a dyad and constructing the infinite out of great and small, instead of treating the infinite as one, is peculiar to him; ...
  2. (music) Any set of two different pitch classes.
  3. A pair of things standing in particular relation; dyadic relation.
    • "For each individual in a specific dyad (i.e., mother-offspring, offspring-father, sibling-sibling),..." Debra Lieberman, John Tooby, and Leda Cosmides - The evolution of human incest avoidance mechanisms: an evolutionary psychological approach, p. 20
  4. (chemistry) An element, atom, or radical having a valence or combining power of two.
  5. (biology) A secondary unit of organisation consisting of an aggregate of monads.

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