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### Curve

The ancient definition of a *curve* is that it is the path traced by a moving point.

##### Explanation

In mathematics the sharp, angular and the straight may all be curves. A *closed curve* is then the one whose end point is the same as its beginning point. If it does not pass to the same point more than once it is called a *simple closed curve*.

Circles, triangles, rectangles, polygons, etc. are all simple closed curves. Drawn on a piece of paper they divide it into an inside and outside. This fact is stated by one of the fundamental theorems of topology.