However, abstracting from
this, we define mathematically a relation R from A to B as an arbitrary subset
of A × B If (a, b) ∈ R, we say that a is related to b under the relation R and we write as
a R b In general, (a, b) ∈ R, we do not bother whether there is a recognisable
connection or link between a and b As seen in Class XI, functions are special kind of
relations