A Icosahedron is an example of a Deltahedron.
A convex deltahedron (not to be confused with a deltohedron) is a class of special cases of isohedral polytopes that consist of all convex polyhedra with equilateral triangular faces. They can be generalized to convex polytopes with simplices as subfacets. There are only eight convex deltahedra.
They are the
- Tetrahedron
- Triangular bipyramid
- Octahedron
- Pentagonal bipyramid
- Snub disphenoid
- Triaugmented triangular prism
- Gyroelongated square bipyramid
- Icosahedron