Pyramid
Triangle
A tetrahedron = triangle based pyramid.
By its very nature of being a triangle, and a 2D shape, a triangle cannot have four plane faces. However, a tetrahedron is a polyhedron made up of four triangular faces.
A tetrahedron is the smallest possible polyhedron: a closed 3-d shape with polygonal faces. It has 4 triangular faces, 4 vertices and 6 edges. It is also known as a triangle-based pyramid.
Regular Tetrahedron
four triangle faces.
tetrahedron
A pyramid has a variable number of triangular faces. The base of a triangle can be practically any regular shape, starting with a triangle. Technically a pyramid can have four or more triangles as faces.
The answer is a polyhedron
A pyramid.
a pyramid
The analogy for "square: triangle" is "cube: tetrahedron." Just as a square is a two-dimensional shape with four equal sides, a triangle is a three-dimensional shape with three vertices. Similarly, a cube is a three-dimensional shape with six equal square faces, while a tetrahedron is a three-dimensional shape with four triangular faces. Both pairs represent geometric shapes with increasing dimensions and different characteristics.