Finite geometry
Finite geometry is a branch of combinatorics. Contrary to the familiar Euclidean geometry in which a line contains infinitely many points, a finite geometry is any geometric system that has only a finite number of points. Examples include finite projective spaces and finite affine spaces, generalized polygons, finite Möbius planes and finite Laguerre planes. It has applications to groups, codes, graphs, designs and permutation polynomials, such as to extremal graph and theory, Latin squares and maximum distance separable codes.