Definition#
A relation \(\rho\) on the set \(S\) is symmetric if \(a\rho b\) implies \(b \rho a\).
Example#
Define \(\rho\) via \(a \rho b\) if and only if \(\left| a-b \right| \leq 10\). Then \(\rho\) is symmetric.
Source#
Gregory T. Lee. Abstract Algebra. 1st ed. Springer Cham, 2018. pp. 6.
