From Ancient Greek δυάς (duás), δυάδ- (duád-) from δύο (dúo, “two”), from Proto-Indo-European *duwó, *duwéh₃ (*dwóh₁). The mathematics sense was coined by Josiah Willard Gibbs in 1884 in the second half of his book Elements of Vector Analysis.
dyad (plural dyads)
- 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; ...
- 2019 January 29, Tom Bissell, “An Anti-Facebook Manifesto”, in New York Times:
- McNamee describes their grip on the company as “the most centralized decision-making structure I have ever encountered in a large company.” Their power dyad is possible only because Facebook’s “core platform,” as McNamee puts it, is relatively simple: It “consists of a product and a monetization scheme.”
- (sociology) Two persons in an ongoing relationship; dyadic relationship.
- "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
- (sociology) The relationship or interaction itself in reference to a couple.
- (music) Any set of two different pitch classes.
- (chemistry) An element, atom, or radical having a valence of or combining power of two.
- (biology) A chromosome structure, usually X- or V-shaped, consisting of two condensed sister chromatids joined by a centromere.
- (biology) A secondary unit of organisation consisting of an aggregate of monads.
- (mathematics) A tensor of order two and rank one.
- (group) monad, duad/dyad, triad, tetrad, pentad, hexad, hebdomad/heptad, ogdoad/octad, ennead/nonad, decad/decade, hendecad, dodecad/duodecade, chiliad
- ^ “dyad”, in The American Heritage Dictionary of the English Language, 4th edition, Boston, Mass.: Houghton Mifflin, 2000, →ISBN.