Assertion: tetrahedron's face | /r/HasProperty | the base
Facets:
Source sentences:
text: A tetrahedron (regular tetrahedron) is a special case of the triangular pyramid that has four equivalent equilateral triangular faces - the base and the other three sides.
text: In the applet, hold the tetrahedron still, with one face (base) furthest away from you, and a vertex closest.
text: A polyhedron with v vertices, e edges, and f faces can be the base on a polyhedral pyramid with v+1 vertices, e+v edges, f+e faces, and 1+f cells.