Cardinality of Set of Bijections

Theorem
Let $S$ and $T$ be sets such that $\left|{S}\right| = \left|{T}\right| = n$.

Then there are $n!$ bijections from $S$ to $T$.

Proof
Follows directly from Cardinality of Set of Injections and Equivalence of Mappings between Sets of Same Cardinality.