A icosahedron.
An icosahedron is in fact not a polygon at all, but a polyhedron. As a polyhedron it is regular however. The regular icosahedron is one of only five possible regular polyhedra. It has 20 faces, each of which is an equilateral triangle.
icosahedron
Icosahedron is a 20 sided polygon.
A 20-sided polyhedron is an icosahedron. A 20-sided polygon is an icosagon.
Icos- Icosagon - 20 sided polygon Icosahedron - 20-faced polyhedron
an icosahedron (icosagon) is a regular polyhedron with 20 identical equilateral triangular faces
20
Well, honey, you're gonna need 20 short isosceles triangles to build that fabulous Icosahedron. Each face of the Icosahedron is made up of an isosceles triangle, and there are 20 faces in total. So, do the math and get building, darling!
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A 20-sided flat figure (polygon) is called an icosagon. If it is a solid figure--three-dimensional--it is an icosahedron.
An icosagon is a two-dimensional polygon, not a three-dimensional figure. An icosagon has 20 sides - while an icosahedron has 20 faces.