# Today I Learned

Some of the things I've learned every day since Oct 10, 2016

## 77: Mapping Continuity (Topology)

December 28, 2016

Posted by on In topology, a mapping between topological spaces is **continuous** if the pre-image of every open subset of is itself an open subset of .

(An equivalent condition/definition is that the pre-image of every *closed* subset of is itself a closed subset of .)

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