A pyramid.
a pyramid
A triangular pyramid. It has triangles on its 3 sides and a triangle on the bottom for a base.
A 3D shape with one base and three faces can only have triangular faces.
A triangular base pyramid would fit the description.
The simplest such shape is PYRAMID.
This would be a triangular prism.
A 3D shape with all triangular faces can be a tetrahedron pyramid.
triangular prisom
An icosahedron.
A triangular pyramid.
square based pyramid
An octagonal pyramid has eight triangles on an octagonal base. An octahedron can also be made by putting a square pyramid on another inverted square pyramid. This shape has just eight triangles and no others.