: an aspect or quality (as resemblance) that connects two or more things or parts as being or belonging or working together or as being of the same kind <the relation of time and space>; specifically: a property (as one expressed by is equal to, is less than, or is the brother of) that holds between an ordered pair of objects
: the referring by a legal fiction of an act to a prior date as the time of its taking effect —usually used with back
a (1): a person connected by consanguinity or affinity :relative(2): a person legally entitled to a share of the property of an intestate
: an aspect or quality (as resemblance or causality) that connects two or more things or parts as being or belonging or working together, as being of the same kind, or as being logically connected <the strong relation between genotype and phenotype—Anne M. Glazier et al>
: the attitude or stance which two or more persons or groups assume toward one another <race relations>
a: the state of being mutually or reciprocally interested (as in social matters) brelationspl:sexual intercourse<testified that relations had occurred—Newsweek>
In logic, a relation R is defined as a set of ordered pairs, triples, quadruples, and so on. A set of ordered pairs is called a two-place (or dyadic) relation; a set of ordered triples is a three-place (or triadic) relation; and so on. In general, a relation is any set of ordered n-tuples of objects. Important properties of relations include symmetry, transitivity, and reflexivity. Consider a two-place (or dyadic) relation R. R can be said to be symmetrical if, whenever R holds between x and y, it also holds between y and x (symbolically, (x) (y) [Rxy Ryx]); an example of a symmetrical relation is x is parallel to y. R is transitive if, whenever it holds between one object and a second and also between that second object and a third, it holds between the first and the third (symbolically, (x) (y) (z ) [(Rxy Ryz) Rxz]); an example is x is greater than y. R is reflexive if it always holds between any object and itself (symbolically, (x) Rxx); an example is x is at least as tall as y since x is always also at least as tall as itself.