# Definition:Relation Segment

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## Definition

Let $X$ be a set.

Let $R$ be a relation on $X$.

Let $x \in X$.

Then the $R$-segment of $x$, denoted by $x^R$, is defined by:

$x^R := \left\{ {y \in X: \left({y, x}\right) \in R}\right\}$