&gt; Examples of binary relations are binary operations (like +,–,⋅,&#x2F;) on N,Z,Q,R,C,Rn, … etc. (where defined), since functions are special cases of relations, or, the order relations &lt;,≤,&gt;,≥ on R, for instance.<p>A function of two variables is a ternary relation, not a binary relation. &#x2F;pedant