dyadic predicate

In logic, a dyadic relation is a set of ordered pairs. It's a fundamental concept within the predicate calculus, which deals with propositions that involve properties of individuals or relations between them.

A dyadic predicate, unlike a monadic (one-place) predicate that describes a property of a single individual (e.g., "Socrates is wise"), describes a relationship between two individuals. For example, "Tom is a son of John" uses a dyadic predicate "is a son of" with "Tom" and "John" as its arguments.12

Dyadic relations can be classified by properties such as symmetry (if R holds between x and y, it also holds between y and x), transitivity (if R holds between x and y, and y and z, it also holds between x and z), and reflexivity (R always holds between an object and itself).3