(mathematics) a branch of mathematics that investigates those properties of figures that are invariant when projected from a point to a line or plane

(geometry, mathematical analysis) The study of geometry, especially geometric structures on differentiable manifolds, using techniques from calculus, linear algebra and multilinear algebra.

(geometry) The subbranch of geometry that investigates geometrical figures via the mathematical properties of their representations in a coordinate system.

(mathematics) A recent branch of geometry that can be described as a piecewise linear version of real algebraic geometry.

(mathematics, geometry) The branch of differential geometry that concerns Riemannian manifolds; an example of a geometry that involves Riemannian manifolds. / Elliptical or spherical geometry.

(mathematics, physics) A version of C*-algebra which does away with commutativity, and the geometry which would be generated by/associated with such a modified algebra.

(geometry) A type of geometry that rejects the parallel postulate. Given a straight line L and a point P not on the line, more than one straight line can be drawn through P without intersecting L.

(geometry) The branch of geometry concerned with inversion transformations, specifically circle inversions in the Euclidean plane, but also as generalised in non-Euclidean and higher-dimensional spaces.

The study of figures having parts that lie in a singular plane.

The geometry of empty spacetime around a rotating uncharged axially-symmetric black hole with a spherical event horizon.