An eight-sided polygon is called an octagon. It has eight straight edges and eight angles, with the most common example being a regular octagon, where all sides and angles are equal. A familiar representation of an octagon is a stop sign, which is typically red and features an octagonal shape. Overall, octagons can vary in size and appearance, but they maintain their eight-sided characteristic.
It is a quadrilateral.
a triangle.
A nonagon is a nine-sided polygon.
It looks like a square with a triangle on top of it.
An octogon- like a stop sign
A polygon
it look like a fifty sided shape
The base would be an octagon, or an eight sided polygon.
Like this
see related link below to see the 20 sided polygon
polyhedron
It is a seven-sided polygon
The Pentagon.
It is a quadrilateral.
a triangle.
It looks like a circle
Join up the hour-markers on a clock face and you will have a dodecagon - a 12 sided polygon.