# Tag Info

A relation $R$ on a set $A$ is any subset of $A\times A$, i.e. any set of ordered pairs $(x,y)$ such that both $x$ and $y$ belong to $A$. Often we write $x\mathrel R y$ instead of $(x,y)\in R$. Typical examples are partial orders, e.g. the relation $\le$ on $\mathbb N$ and equivalence relation, e.g. the relation $=$ on $\mathbb N$.