Dimension

1. Measure in a single line, as length, breadth, height, thickness, or circumference; extension; measurement; -- usually, in the plural, measure in length and breadth, or in length, breadth, and thickness; extent; size; as, the dimensions of a room, or of a ship; the dimensions of a farm, of a kingdom.
2. Extent; reach; scope; importance; as, a project of large dimensions.
3. (Math.) The degree of manifoldness of a quantity; as, time is quantity having one dimension; volume has three dimensions, relative to extension.
4. (Alg.) A literal factor, as numbered in characterizing a term. The term dimensions forms with the cardinal numbers a phrase equivalent to degree with the ordinal; thus, a2b2c is a term of five dimensions, or of the fifth degree.
Space of dimension ,
extension that has length but no breadth or thickness; a straight or curved line.
Space of two dimensions ,
extension which has length and breadth, but no thickness; a plane or curved surface.
Space of three dimensions ,
extension which has length, breadth, and thickness; a solid.
Space of four dimensions ,
as imaginary kind of extension, which is assumed to have length, breadth, thickness, and also a fourth imaginary dimension. Space of five or six, or more dimensions is also sometimes assumed in mathematics.