A solid with flat faces (from Greek poly- meaning "many" and -edron meaning "face").
Example: Pyramids and prisms
Each flat surface (or "face") is a polygon.
A polyhedron is a 3D figure made up of many sides or faces. In a polyhedron, several polygonal faces meet at a corner (vertex). Types of polyhedra by number of faces are tetrahedron, pentahedron, hexahedron, octahedron, decahedron. The more faces there are on a polyhedron, the more closely it approximates to a sphere. Knowledge of the properties of polyhedra is needed in crystallography and stereochemistry to determine the shapes of crystals and molecules. There are only five types of regular polyhedron (with all faces the same size and shape), as was deduced by early Greek mathematicians; they are the tetrahedron (four equilateral triangular faces), cube (six square faces), octahedron (eight equilateral triangles), dodecahedron (12 regular pentagons) and icosahedron (20 equilateral triangles).
It is a geometric solid that has flat faces and straight edges. They are named according to the number of faces present in the solid. There are many different types of it, like tetrahedron (4), pentahedron (5), hexahedron (6), heptahedron (7), triacontahedron (30), and many more. The edges have two distinctive properties, and that is it just joined two vertices and faces. It is also a three-dimensional figure, that is make by finite number of faces, which are part of planes.