Is all pyramids are tetrahedrons

No, not all pyramids are tetrahedrons. A pyramid is a three-dimensional shape with a polygonal base and triangular faces that meet at a single point called the apex. A tetrahedron is a specific type of pyramid that has a triangular base and four triangular faces. Thus, while all tetrahedrons are pyramids, not all pyramids are tetrahedrons, as they can have various polygonal bases with different numbers of sides.