# 📝Binary relation properties

Reflexive:

for every x, x ≤ x

as a graph:

Symmetric:

For every x and y, if x ≤ y then y ≤ x

if there is an edge between vertices, there is an edge in the opposite direction

as a graph

Antisymmetric:

If x ≤ y and y ≤ x, then x = y

if there is an edge between vertices, there is no other edge in the opposite direction

as a graph:

\begin{tikzcd} a \arrow[loop left] \arrow[r] & b \end{tikzcd}

Asymmetric:

$\forall a,b \in X : a R b \rightarrow \lnot (b R a)$ (including $a=b$)

A relation is asymmetric iff it is both antisymmetric and irreflexive

as a graph:

Transitive:

If x ≤ y and y ≤ z, then x ≤ z

as a graph:

Connexity (connex relation):

the relation is defined between all pairs of elements

$\forall x, y \in X, x R y \lor y R x$

Semiconnexity (semiconnex relation):

the relation is defined between all pairs of

*distinct*elements$\forall x, y \in X, x \ne y \rightarrow x R y \lor y R x$

## Backlinks

- 📝 § Math