Each side is called a face.
A twenty sided, 2D figure is called an icosagon.
The vertex of an angle
A two-dimensional figure is a polygon. The eight sides means that it uses the prefix octa- (meaning eight) to form the name octagon.
A regular hexagon.
Quadrilateral is the name fr a geometric figure with 4 sides.
The correct name would be a "tetradecagon"
It is called a Tetrahedron.
It is called a heptagon or a septagon,
A 5-sided figure is called a "Pentagon".
For a Polygon, "Poly" means "many" or "a number of"; "gon", roughly means "angles". So a poloygon is a figure with a number of angles between its sides. . If the number of sides is definite then "poly" is replaced by a word meaning that number.
a 12 sided figure is called a dodecagon
I think a circle
The geometric name for the shape of a Hula Hoop or a smoke ring (which are hollow) is a torus. If the shape is solid, like a donut or a ring, it's called a toroid.