dimension (physics)

dimension in physics, an expression of the character of a derived quantity in relation to fundamental quantities, without regard for its numerical value. In any system of measurement, such as the metric system, certain quantities are considered fundamental, and all others are considered to be derived from them. Systems in which length ( L ), time ( T ), and mass ( M ) are taken as fundamental quantities are called absolute systems. In an absolute system force is a derived quantity whose dimensions are defined by Newton's second law of motion as ML / T² , in terms of the fundamental quantities. Pressure (force per unit area) then has dimensions M/LT² ; work or energy (force times distance) has dimensions ML² / T² ; and power (energy per unit time) has dimensions ML² / T³ . Additional fundamental quantities are also defined, such as electric charge and luminous intensity. The expression of any particular quantity in terms of fundamental quantities is known as dimensional analysis and often provides physical insight into the results of a mathematical calculation.

di·men·sion / diˈmenchən/ • n. 1. an aspect or feature of a situation, problem, or thing: sun-dried tomatoes add a new dimension to this sauce. 2. (usu. dimensions) a measurable extent of some kind, such as length, breadth, depth, or height: the final dimensions of the pond were 14 ft. x 8 ft. | the drawing must be precise in dimension. ∎  a mode of linear extension of which there are three in space and two on a flat surface, which corresponds to one of a set of coordinates specifying the position of a point. ∎  Physics an expression for a derived physical quantity in terms of fundamental quantities such as mass, length, or time, raised to the appropriate power (acceleration, for example, having the dimension of length × time⁻²). • v. [tr.] (often be dimensioned) cut or shape (something) to particular measurements. ∎  mark (a diagram) with measurements: [as adj.] (dimensioned) draw a dimensioned front elevation. DERIVATIVES: di·men·sion·al / -chənl/ adj. [in comb.] multidimensional scaling.di·men·sion·al·i·ty / diˌmenchəˈnalətē/ n.di·men·sion·al·ly / -chənl-ē/ adj. di·men·sion·less adj.