MathGloss

A topological space is a set $X$ together with a collection $T$ of subsets of $X$. The elements of $T$ are called the open sets and they satisfy the following properties:

1. $X\in T$ and $\emptyset \in T$.
2. Arbitrary unions of open sets are open.
3. Finite intersections of open sets are open.

$T$ is called a topology on $X$.

Wikidata ID: Q179899

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