dyad

UK: /ˈdaɪæd/ US: (dī′ad)

WordReference Random House Unabridged Dictionary of American English © 2026

dy•ad  (dī′ad), n. 

1. a group of two;
   couple;
   pair.
2. Biochemistry, Cell Biology
   • a secondary morphological unit, consisting of two monads:
     a chromosome dyad.
   • the double chromosomes resulting from the separation of the four chromatids of a tetrad.
3. Chemistry an element, atom, or group having a valence of two. Cf. monad, triad (def. 2a).
4. Mathematics two vectors with no symbol connecting them, usually considered as an operator.
5. Sociology
   • two persons involved in an ongoing relationship or interaction.
   • the relationship or interaction itself.

adj. 

6. of two parts;
   dyadic.

• Greek dyad- (stem of dyás) pair, equivalent. to dý(o) two + -ad- -ad¹
• 1665–75

Collins Concise English Dictionary © HarperCollins Publishers::

dyad / ˈdaɪæd/ noun

1. an operator that is the unspecified product of two vectors. It can operate on a vector to produce either a scalar or vector product
2. an atom or group that has a valency of two
3. a group of two; couple

Etymology: 17th Century: from Late Latin dyas, from Greek duas two, a pair