Simplify the following text for a Grade 8 native English-speaking person.
Original: A polygon is a polytope in two dimensions , a polyhedron in three dimensions , and so on in higher dimensions ( such as a polychoron in four dimensions ) .
Simplified: A polytope is figure in geometry . It is a generalisation of the polygon in two dimensions , and the polyhedron in 3 dimensions , to any number of dimensions .