51Mxx Real and complex geometry
 51M04 Elementary problems in Euclidean geometries
 51M05 Euclidean geometries (general) and generalizations
 51M09 Elementary problems in hyperbolic and elliptic geometries
 51M10 Hyperbolic and elliptic geometries (general) and generalizations

51M15 Geometric constructions
(1)
 51M16 Inequalities and extremum problems (For convex problems, see 52A40)
 51M20 Polyhedra and polytopes; regular figures, division of spaces [See also 51F15]
 51M25 Length, area and volume [See also 26B15]
 51M30 Line geometries and their generalizations [See also 53A25]
 51M35 Synthetic treatment of fundamental manifolds in projective geometries (Grassmannians, Veronesians and their generalizations) [See also 14M15]
 51M99 None of the above, but in this section