Simplicial homology arose as a way to study topological spaces whose building blocks are "n"-simplices, the "n"-dimensional analogs of triangles. This includes a point (0-simplex), a line segment (1-simplex), a triangle (2-simplex) and a tetrahedron (3-simplex). By definition, such a space is homeomorphic to a simplicial complex (more precisely, the geometric realization of an abstract simplicial complex). Such a homeomorphism is referred to as a "triangulation" of the given space. Many topological spaces of interest can be triangulated, including every smooth manifold (Cairns and Whitehead).