### 51-XX Geometry,

{For algebraic geometry, See 14-XX}
- 51-00 General reference works (handbooks, dictionaries, bibliographies, etc.)
- 51-01 Instructional exposition (textbooks, tutorial papers, etc.)
- 51-02 Research exposition (monographs, survey articles)
- 51-03 Historical (must be assigned at least one classification number from 01-XX)
- 51-04 Explicit machine computation and programs (not the theory of computation or programming)
- 51-06 Proceedings, conferences, collections, etc.
- 51Axx Linear incidence geometry
- 51Bxx Nonlinear incidence geometry
- 51C05 Ring geometry (Hjelmslev, Barbilian, etc.)
- 51Dxx Geometric closure systems
- 51Exx Finite geometry and special incidence structures
- 51Fxx Metric geometry
- 51G05 Ordered geometries (ordered incidence structures, etc.)
- 51Hxx Topological geometry
- 51Jxx Incidence groups
- 51Kxx Distance geometry
- 51Lxx Geometric order structures, see also {53C75}
- 51Mxx Real and complex geometry
- 51Nxx Analytic and descriptive geometry
- 51P05 Geometry and physics (should also be assigned at least one other classification number from Sections 70--86)

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