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### Fundamental theorem of topology

One of the **fundamental theorems** of topology reads:

A simple closed curve in the plane divides the plane into exactly two domains.

##### Jordan curve theorem

All simple closed loops in a plane divide this plane into two coherent separated parts where the loop forms the common border. One of these parts is bounded (the inside of the loop) and the other is not limited and is called the outside.

## HistoryThe theorem is intuitively clear, but was first proven by the French mathematician Camille Jordan (1838 - 1922). |