a cone
A shape with 8 sides is an octagon.
An octagon.
A five-sided geometric shape is a pentagon.
I would call it an irregular octagon, or an irregular 8-sided polygon.
A regular octagon
a cone
An Octagon.
An octagon
A shape with 8 sides is an octagon.
An Octagon
An octagon.
an octogon
A regular octagon
A polygon with 1,000 sides is known as a chiliagon. A hectogon is a polygon that has 100 sides, and a polygon with 8 sides is called an octagon.
A five-sided geometric shape is a pentagon.
Hexadecagon (16 sides) and Octadecagon (18 sides) both fit. Am I missing something?