\begin{definition}[Definition:Injective Space]
Let $Z = \left({S, \tau_1}\right)$ be a topological space.
Then $Z$ is '''injective (space)''' {{iff}}
:for all topological spaces $X = \left({H, \tau_2}\right)$
:and for all continuous mappings $f:H \to S$
:and for all topological spaces $Y = \left({T, \tau_3}\right)$ such that $X$ is topological subspace of $Y$:
:there exists a continuous mapping $g:T \to S$: $g \restriction H = f$
\end{definition}