General topology
In mathematics, general topology or point set topology is that branch of topology which studies elementary properties of topological spaces and structures defined on them.
Other main branches of topology are algebraic topology and differential topology.
It's in general topology that basic notions, such as:
Some standard books on general topology include:
are defined and theorems about them are proved.
Other more advanced notions also appear, but are usually related directly to these fundamental concepts, without reference to other branches of mathematics.
Standard references