(mathematics) the locus of points in the Euclidean plane that satisfies some geometric or algebraic definition; a curve in a plane (as opposed to higher-dimensional space)

(mathematics) Two-dimensional Euclidean space.

(mathematics) a representation of the space of complex numbers

(parapsychology, Theosophy) A supernatural plane of existence, propounded by esoteric philosophies, some religious teachings, and New Age thought.

(geometry) An angle formed by two intersecting straight lines.

(differential geometry) Given a point P on a surface M, the tangent plane of M at point P, denoted by T_P(M), is the plane passing through P which contains the tangent lines of all the curves on M passing through P.

An aircraft that flies alongside another, to advise or photograph it while experimental flights are being carried out.

(astronomy) The surface (plane) that contains the orbit of a planet in a solar system.

(astronomy) The surface (plane) that contains an orbit.

(mathematics) A topological space homeomorphic to a plane (or open disk) and equipped with a hyperbolic metric.