Understand that 'tetrahedron' refers to a precise mathematical shape, not any four-faced object. Studying solids, I learned a tetrahedron is a specific type of polyhedron.
Pro Tip 2/3
Not Always Pyramid
While tetrahedrons resemble pyramids, they precisely have four triangular faces, unlike some pyramids. A pyramid in Egypt isn't a tetrahedron, as its base isn't triangular.
Pro Tip 3/3
Regular vs. Irregular
A regular tetrahedron has equal sides; irregular ones don't, but both share the four-face characteristic. A regular tetrahedron is like a 3D equilateral triangle.