A Concave is a polygon in which one or more of the interior angles is greater than 180 degrees.

As a result it looks like one vertex has been pushed inward.

The cave is created by the interior angle greater than 180 degrees.

A line can be drawn through a concave polygon that will intersect the polygon in more than two places.

A Polygon that does not have an interior angle greater than 180 degrees.

The vertices appear to be pointing outward.

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