An octahedron, which looks like 2 pyramids glued bottom to bottom.
A 20-sided polyhedron is called an icosahedron. It has 20 equilateral triangle faces, 30 edges, and 12 vertices. It is a regular convex polyhedron with rotational symmetry.
No, a decahedron is a ten-sided polyhedron, which is a geometric shape. It is not a naturally occurring shape in nature.
A "prism". Note: Prisms actually have five sides. There is no three-sided polyhedron.
A three-dimensional trapezium is called a trapezoid. It is a four-sided figure with at least one pair of parallel sides.
solid, polyhedron, and prism for the block looking thing
A polyhedron with 20 faces is called an icosahedron.
In general, any 10-sided polyhedron is called a decahedron. With 10 regular triangles for faces, you may have a pentagonal bipyramid.
nonahedron
A one-hundred sided polyhedron is called a hecatohedron, comming from the Greek Hecto- meaning one-hundred and -hedronmeaning a three-dimensional figure.
A 20-sided polyhedron is called an icosahedron. It has 20 equilateral triangle faces, 30 edges, and 12 vertices. It is a regular convex polyhedron with rotational symmetry.
Octohedron
I believe it called a Bucky Ball. After Buckminster Fuller.
a polyhedron (if the shape is 3 dimensional) a polygon if it is a planar shape.
A 120-sided polyhedron is a hecatonicosahedron.
A 2D seven sided figure is called a heptagon. A 3D seven faced polygon is called a heptahedron.
A shape in 2D with n sides is called an n-gon. In higher dimensions, a shape with n sides is called an n-sided polyhedron.
Decahedron :)