\begin{definition}[Definition:Isometry (Metric Spaces)/Definition 1]
Let $M_1 = \tuple {A_1, d_1}$ and $M_2 = \tuple {A_2, d_2}$ be metric spaces or pseudometric spaces.
Let $\phi: A_1 \to A_2$ be a bijection such that:
:$\forall a, b \in A_1: \map {d_1} {a, b} = \map {d_2} {\map \phi a, \map \phi b}$
Then $\phi$ is called an '''isometry'''.
That is, an '''isometry''' is a distance-preserving bijection.
\end{definition}