Triangle
A 3-sided figure is called a triangle.
A ten sided figure is called a Decagon. ( i think that's how you spell it. )
In 2 dimensions, a regular 5 sided figure is a pentagon. In 3 dimensions, there is no regular sided 5 sided figure. The tetrahedron is a regular 4 sided figure and a cube is a regular 6 sided figure.
A three-sided, two-dimensional polygon is called a "triangle".
A seven sided figure is called a heptagon.
An eight sided figure is called an octagon.
A four sided figure is called a quadrilateral.
A 12-sided figure is called a dodecagon.
A six-sided plane figure is called a hexagon.
A six-sided plane figure is called a hexagon.
Square pyramid.
A 12 sided figure is called a dodecagon. A 3-dimensional shape with 12 faces is called a dodecahedron.