Binary relations on sets

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Sorry for such a query. But can a relation be both antisymmetric as well as asymmetric? for ex. is this relation {(3,4),(5,6)} both antisymmetric and asymmetric.

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Yes, although somewhat trivially.

A relation $R$ is asymmetric iff, for any $x,y$ in the domain, $xRy\Rightarrow \neg yRx$. It is antisymmetric iff $xRy \wedge yRx \Longrightarrow y=x$. However, for an asymmetric relation $R$, the condition $xRy\wedge yRx$ is always false, which means the condition for being an antisymmetric relation is (vacuously) true.

Therefore, every asymmetric relation is also antisymmetric. (But not every antisymmetric relation is asymmetric.)