If the faces are flat, it's a line.
Icosahedron
Isosceles TetrahedronA solid with four faces is a tetrahedron. Each of the faces is a triangle. If all the triangles are congruent, you have an isosceles tetrahedron.
a cylinder a cylinder
polyhedra
an edge
An edge.
an edge
The edge.
If the faces are flat, it's a line.
A vertex is the name of a corner on a solid where three or more faces meet (plural = vertices).
a vortex
an edge
That is a vertex.
A corner
The vertex or apex
Icosahedron