Euclidean topology

In mathematics, and especially general topology, the Euclidean topology is an example of a topology given to the set of real numbers, denoted by R. To give the set R a topology means to say which subsets of R are "open", and to do so in a way that the following axioms are met:

1. The union of open sets is an open set.
2. The finite intersection of open sets is an open set.
3. The set R and the empty set Ø are open sets.