dimensionless

Adjective

1. Lacking dimensions.
   • To Heav'n thir prayers / Flew up, nor miſsd the way, by envious windes / Blow'n vagabond or fruſtrate: in they paſsd / Dimentionleſs through Heav'nly dores; […] - 1674, John Milton, “Book XI”, in Paradise Lost. […], 2nd...
   • Extended objects may be separated by dimensionless points; but dimensionless points cannot be separated, but by some real distance, or something really extended. - 1771, William Kenrick, A Lecture on Perpetual Motion,...
   • 1930, E. E. Smith, Skylark Three, Fantasy Press, 1948, Chapter 3, They saw the utter, absolute darkness of the complete absence of all light; and upon that indescribable blackness they beheld superimposed the almost...

   Synonyms: adimensional

2. Of a physical constant: lacking units.
   • Iron has a density of 7.8 grams per cubic centimeter: its dimensionless relative density is 7.8.
   • A strain is a dimensionless quantity and is usually expressed in percentages. Typical measures for strain are less than 2 mm/m for steel and are often expressed in micro-strain units. One microstrain is the strain...