A
binary relation [math]R
[/math] on a
set [math]A
[/math] is
symmetric if
for all pairs of
elements [math]x
[/math] and
[math]y \href{/cs2800/wiki/index.php/%E2%88%88}{∈} A
[/math] with
[math]\href{/cs2800/wiki/index.php/XRy}{xRy}
[/math], we also have
[math]\href{/cs2800/wiki/index.php/XRy}{yRx}
[/math].
In a picture, this means that every edge from [math]x
[/math] to [math]y
[/math] has a corresponding edge from [math]y
[/math] back to [math]x
[/math].
