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[dih-men-shuh n, dahy-] /dɪˈmɛn ʃən, daɪ-/
  1. a property of space; extension in a given direction:
    A straight line has one dimension, a parallelogram has two dimensions, and a parallelepiped has three dimensions.
  2. the generalization of this property to spaces with curvilinear extension, as the surface of a sphere.
  3. the generalization of this property to vector spaces and to Hilbert space.
  4. the generalization of this property to fractals, which can have dimensions that are noninteger real numbers.
  5. extension in time:
    Space-time has three dimensions of space and one of time.
Usually, dimensions.
  1. measurement in length, width, and thickness.
  2. scope; importance:
    the dimensions of a problem.
unit (def 6).
magnitude; size:
Matter has dimension.
  1. a magnitude that, independently or in conjunction with other such magnitudes, serves to define the location of an element within a given set, as of a point on a line, an object in a space, or an event in space-time.
  2. the number of elements in a finite basis of a given vector space.
Physics. any of a set of basic kinds of quantity, as mass, length, and time, in terms of which all other kinds of quantity can be expressed; usually denoted by capital letters, with appropriate exponents, placed in brackets:
The dimensions of velocity are [LT−1].
dimensions, Informal. the measurements of a woman's bust, waist, and hips, in that order:
The chorus girl's dimensions were 38-24-36.
verb (used with object)
to shape or fashion to the desired dimensions:
Dimension the shelves so that they fit securely into the cabinet.
to indicate the dimensions of an item, area, etc., on (a sketch or drawing).
Origin of dimension
late Middle English
1375-1425; late Middle English dimensioun (< Anglo-French) < Latin dīmēnsiōn- (stem of dīmēnsiō) a measuring, equivalent to dīmēns(us) measured out (past participle of dīmētīrī, equivalent to dī- di-2 + mētīrī to measure) + -iōn- -ion
Related forms
dimensional, adjective
dimensionality, noun
dimensionally, adverb
dimensionless, adjective
multidimensional, adjective
nondimensioned, adjective
undimensioned, adjective
2b. range, extent, magnitude. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for dimensionless


(often pl) a measurement of the size of something in a particular direction, such as the length, width, height, or diameter
(often pl) scope; size; extent: a problem of enormous dimensions
aspect: a new dimension to politics
(maths) the number of coordinates required to locate a point in space
  1. the product or the quotient of the fundamental physical quantities (such as mass, length, or time) raised to the appropriate power in a derived physical quantity: the dimensions of velocity are length divided by time
  2. the power to which such a fundamental quantity has to be raised in a derived quantity
(transitive) (mainly US)
  1. to shape or cut to specified dimensions
  2. to mark with specified dimensions
Derived Forms
dimensional, adjective
dimensionality, noun
dimensionally, adverb
dimensionless, adjective
Word Origin
C14: from Old French, from Latin dīmensiō an extent, from dīmētīrī to measure out, from mētīrī
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for dimensionless



late 14c., "measurement, size," from Latin dimensionem (nominative dimensio) "a measuring," noun of action from past participle stem of dimetri "to measure out," from dis- (see dis-) + metiri "to measure" (see measure). Meaning "any component of a situation" is from 1929. Related: Dimensional; dimensions.

Online Etymology Dictionary, © 2010 Douglas Harper
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dimensionless in Medicine

dimension di·men·sion (dĭ-měn'shən, dī-)

  1. A measure of spatial extent, especially width, height, or length.

  2. Scope or magnitude.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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dimensionless in Science
    1. Any one of the three physical or spatial properties of length, area, and volume. In geometry, a point is said to have zero dimension; a figure having only length, such as a line, has one dimension; a plane or surface, two dimensions; and a figure having volume, three dimensions. The fourth dimension is often said to be time, as in the theory of General Relativity. Higher dimensions can be dealt with mathematically but cannot be represented visually.

    2. The measurement of a length, width, or thickness.

  1. A unit, such as mass, time, or charge, associated with a physical quantity and used as the basis for other measurements, such as acceleration.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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