Plane

Plane is a term that in some spiritual and esoteric philosophies is used to refer to a locality or dimension, which can be physical or non-physical. The original source of the word "plane" in this context seems to be the late Neoplatonist Proclus, who frequently used the word platos (πλάτος) meaning "amplitude, breadth, broadness, width", as in the expression en to psuchiko platei.

H. P. Blavatsky defined the word plane as follows:

Plane. From the Latin planus (level, flat) an extension of space or of something in it, whether physical or metaphysical, e.g., a “plane of consciousness”. As used in Occultism, the term denotes the range or extent of some state of consciousness, or of the perceptive power of a particular set of senses, or the action of a particular force, or the state of matter corresponding to any of the above.