The set of all possible points; made up of infinite planes.
A geometric structure that generalizes the affine properties of Euclidean space.
A collection of vectors which means that the space is an additive Abelian group and, in addition, its elements can be multiplied by scalars.
A space X is metric if there is defined a real non-negative function of two variables d(A, B).
Every point has a collection of neighborhoods to which it belongs.