Included here are pages that discuss teaching aids about measurement formulas, axioms and drawing methods pertaining to geometric figures.

Webpages that discuss the topic of geometry without offering teaching materials or resources should be placed in the parent category of Geometry.

## Algebraic Geometry

Please observe the following suggestion when submitting sites to the category: a. Submit the mathematician/researcher''s name as the title (in last name, first name format) b. Description should include, in this order: place of work, field of research or interest, content of the site.

## Computational Geometry

Computational geometry is in some sense the intersection of computer science and geometry, studying efficient algorithms for solving geometric problems.

## Differential Geometry

Differential geometry is a mathematical discipline that uses the methods of differential and integral calculus, as well as linear and multilinear algebra, to study problems in geometry.

## Education

Geometry education is about teaching ideas, lesson plans, curriculum for students in a class that teaches about forms and shapes that can be measured.
Included here are pages that discuss teaching aids about measurement formulas, axioms and drawing methods pertaining to geometric figures.

Webpages that discuss the topic of geometry without offering teaching materials or resources should be placed in the parent category of Geometry.

## Events

Conferences, meetings and workshops in Geometry.

## Higher Dimensional

Higher-dimensional geometry considers the properties of figures with four or more dimensions. An object of zero dimensions is a single point. It needs no coordinates. The first dimension takes up the space of a line, and has only one coordinate (the x coordinate). The second dimension takes up the space of a plane, and has two coordinates, x and y. Examples of two-dimensional shapes are circles and squares. The third dimension is all space that we know of, and it uses three coordinates, x, y, and z. Examples of three-dimensional shapes are cubes, spheres, and cones. The fourth dimension is space with an extra dimension beyond the third, and it uses four coordinates, x, y, z, and w. Examples of four-dimensional shapes are the tesseract and the hypersphere.
Submit pages that deal with geometrical shapes or objects within a space of four or more dimensions. Sites about higher-dimensional polytopes in particular should be submitted to Science/Math/Geometry/Polytopes/Higher_Dimensional/.

## Non-Euclidean

The study of geometrical systems which differ from that of Eculid, specifically with respect to the 5th or an equivalent to the Parallel Postulate, which states: If two lines are drawn which intersect a third in such a way that the sum of the inner angles on one side is less than two right angles, then the two lines inevitably must intersect each other on that side if extended far enough. This means that in the Euclidean world that lines that are not parallel must inevitably meet. This is not always true in non-Euclidean geometry. This category may also contain webpages with discussion of the validity or otherwise of these different geometries.

## Open Problems

Open research-level problems in Geometry. Recreational problems and puzzles have their own categories.

## People

Submit sites that are about earlier mathematicians that are no longer living.

## Plane Geometry

Includes webpages that focus exclusively about two dimension figures, such as lines, circles, and polygons.
Please submit sites that deal only with geometric objects within two dimensions, such as lines, circles and polygons.

## Polytopes

Polytopes include polygons (two-dimensional), polyhedra (three-dimensional), polychora (four-dimensional), and their higher dimensional analogs. An n-dimensional polytope is built up from multiple (n-1)-dimensional polytopes. Thus, polyhedra are built up from polygons, and polychora are built up from polyhedra. A regular polytope is composed of regular (n-1)-dimensional polytopes. There are an infinite number of regular convex polygons, five regular convex polyhedra, six regular convex polychora, and three regular convex polytopes for all dimensions five or higher.
Submit sites that discuss polytopes in general, which include regular sided geometric figures in one, two, three, four or more dimensions.

Sites about polyhedra(three dimensional) in particular should be submitted to thePolyhedra category.

Sites about regular shapes in four dimensions or more should be submitted to the Higher Dimensional category.

## Projective

The systems of geometry studying those properties invariant under projection from one point to another. One of the earlier axiomatic systems.

## Publications

Books, eprints, journals, newsletters, preprints and other publications in Geometry.