Certain geometric figures are created by combining circles with other
geometric figures, such as polygons. There are two
simple ways to unite a circle with a polygon. One is inscription, and the
other is circumscription.

When a polygon is inscribed in a circle, it means that each of the
vertices of that polygon
intersects the circle. When a polygon is circumscribed about a circle, it means
that each of the sides of the polygon is
tangent
to the circle. Below these situations are pictured.

Above on the left, the hexagon ABCDEF is
inscribed
in the circle G. On the right, the
quadrilateral
ABCD is circumscribed about the circle E.

Concentric Circles

One more brief topic to introduce is concentric circles. Concentric circles
are circles that have the same center. Just because a circle is inside
another circle doesn't mean they are concentric; they must have the same
point as their center. Any
number of
circles can be concentric to one another, provided that they all share a center.
Below a few are pictured.