Plane
The word plain is an adjective, a noun, and a verb.
As an adjective
As an adjective of the word plane means,
-Completely level
-Completely flat
As a noun
As a noun the word plane means,
-A flat surface on which a straight line joining any two points would wholly lie.
-A level of existence
-A level of thought
-A level of development
As a verb
As a verb the word plane means,
(Of a bird or airborne object)
-Soar without moving the wings
-Glide