Definition
Nonagon
A nonagon is a closed polygon with exactly nine straight sides and nine corners.
Continue from this idea into connected AXIO math.
What it means
Walk once around the boundary and count each straight side. If the count is nine, the shape is a nonagon. The sides may be different lengths, and turning the shape does not change its name.
Remember it
Trace the edge and count to nine: nine sides, one nonagon.
Example
A sign is drawn with nine straight boundary segments. Three are long and six are short, but the boundary still has nine sides, so the sign is an irregular nonagon.
Watch for
A shape with eight straight sides is an octagon, and a closed shape with a curved edge is not a polygonal nonagon.
Common mix-up
Nonagon tells how many sides there are. Regular nonagon adds the extra condition that all sides and all angles are equal.
Exact meaning
A nonagon is a polygon whose boundary consists of exactly nine straight line segments; those segments meet at nine vertices.