In the topology and other related areas of mathematics, T1 spaces and R0 spaces are special types of topological spaces. The T1 and R0 properties are examples of separation axiomas. Definitions
Let X be a topological space and let x and y be in X. We say that x and y can be separated if each point is part of an open set that does not contain the other point.
A T1 space also becomes an accessible space or Fréchet space and a R0 space is also called a symmetrical space. (The term Fréchet space also has a very different meaning in the functional analysis. For this reason, the term T1 space is preferred. There is also a notion of a Fréchet-Urysohn space as a sort of sequential space. The term symmetrical space also has a different meaning).
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