Complex sentence: If the connectedness assumption (in the definition of abstract polytope) is dropped, then we get uniform compounds, which can be split as a union of polyhedra, such as the compound of 5 cubes.
Split into simpler sentences: If the connectedness assumption (in the definition of abstract polytope) is dropped, then we get uniform compounds. Some polyhedra can be split as a union of others, such as the compound of 5 cubes.