Definition:Identification Topology

Definition
Let $\left({S_1, \tau_1}\right)$ be a topological space.

Let $S_2$ be a set.

Let $f: S_1 \to S_2$ be a mapping.

Then there exists a topology $\tau_2$ on $S_2$ such that:
 * $(1): \quad f: S_1 \to S_2$ is a continuous mapping;
 * $(2): \quad \tau_2$ is the finest topology on $S_2$ for which $f: S_1 \to S_2$ is continuous.

That is:
 * $\tau_2 = \left\{{V \in \mathcal P \left({S_2}\right): f^{-1} \left({V}\right) \in \tau_1}\right\}$

This topology $\tau_2$ is the identification topology on $S_2$ with respect to $f$ and $\left({S_1, \tau_1}\right)$.

It is seen to depend both on $f$ and $\tau_1$.

Its existence and uniqueness is clear by recognition of the fact that for any $V \subseteq S_2$, either $f^{-1} \left({V}\right) \in \tau_1$ or $f^{-1} \left({V}\right) \notin \tau_1$.

Identification Mapping
The mapping $f: S_1 \to S_2$ in this context is called the identification mapping.

Also see

 * Final Topology
 * Quotient Topology

Some sources call $\tau_2$ the quotient topology on $S_2$ with respect to $f$ and $\left({S_1, \tau_1}\right)$'''.

This is reasonable, as we can construct the induced equivalence from any mapping $f$ and thence consider the identification topology as the quotient topology.

From Identification Topology Equals the Quotient Topology on Induced Equivalence, it can be seen that they are in fact one and the same thing, but seen from a different angle.