dyad

noun

Etymology: From Ancient Greek δυάς (duás), δυάδ- (duád-) from δύο (dúo, “two”), from Proto-Indo-European *duwó, *duwéh₃ (*dwóh₁). The mathematics sense was coined by American scientist Josiah Willard Gibbs in 1884 in the second half of his book Elements of Vector Analysis.

1. A set of two elements treated as one; a pair.

   “[…] positing a dyad and constructing the infinite out of great and small, instead of treating the infinite as one, is peculiar to him; […]”

   “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.””

2. Two persons in an ongoing relationship; a dyadic relationship.

   “For each individual in a specific dyad (i.e., mother-offspring, offspring-father, sibling-sibling), […]”

   “The southern relationship was a slaveholder-physician dyad, with the slave left outside, unconsulted, uninformed, and with no recourse if she or he was unsatisfied, injured, or killed—a medical nonentity.”

3. The relationship or interaction itself in reference to a couple.
4. Any set of two different pitch classes.
5. An element, atom, or radical having a valence of or combining power of two.
6. A chromosome structure, usually X- or V-shaped, consisting of two condensed sister chromatids joined by a centromere.
7. A secondary unit of organisation consisting of an aggregate of monads.
8. A tensor of order two and rank one.