In mathematics, a plane is any flat, two-dimensional surface. A plane is the two dimensional analogue of a point (zero-dimensions), a line (one-dimension) and a space (three-dimensions). Planes can arise as subspaces of some higher dimensional space, as with the walls of a room, or they may enjoy an independent existence in their own right, as in the setting of Euclidean geometry.
When working in two-dimensional Euclidean space, the definite article is used, the plane, to refer to the whole space. Many fundamental tasks in geometry, trigonometry, and graphing are performed in two-dimensional space, or in other words, in the plane. A lot of mathematics can be and has been performed in the plane, notably in the areas of geometry, trigonometry, graph theory and graphing.
In esoteric cosmology, a plane, other than the physical plane is conceived as a subtle state of consciousness that transcends the known physical universe.
The concept may be found in religious, and esoteric teachings - e.g. Vedanta (Advaita Vedanta), shamanism, Hermeticism, Neoplatonism, Gnosticism, Kashmir Shaivism, Sant Mat/Surat Shabd Yoga, Sufism, Druze, Kabbalah, Theosophy, Anthroposophy, Rosicrucianism (Esoteric Christian), Eckankar, Ascended Master Teachings, etc. - which propound the idea of a whole series of subtle planes or worlds or dimensions which, from a center, interpenetrate themselves and the physical planet in which we live, the solar systems, and all the physical structures of the universe. This interpenetration of planes culminates in the universe itself as a physical structured, dynamic and evolutive expression emanated through a series of steadily denser stages, becoming progressively more material and embodied.
The emanation is conceived, according to esoteric teachings, to have been originated, at the dawn of the universe's manifestation, in The Supreme Being Who sent out - from the unmanifested Absolute beyond comprehension - the dynamic force of creative energy, as sound-vibration ("the Word"), into the abyss of space. On the other hand, it states that this dynamic force is being sent forth, through the ages, framing all things that constitute and inhabit the universe.