Definition of magnitude
1a
: great size or extent
cannot wage a war of such magnitude— A. N. Whitehead the magnitude of an earthquake
2
: the importance, quality, or caliber of something
evil of such magnitude as must, if possible, be prevented— Jane Austen a writer of first magnitude— Richard Plant
3
: a number representing the intrinsic (see intrinsic sense 1a) or apparent brightness of a celestial (see celestial entry 1 sense 2) body on a logarithmic scale in which an increase of one unit corresponds to a reduction in the brightness of light by a factor of 2.512
4
: a numerical quantitative measure expressed usually as a multiple of a standard unit
5
: the intensity of an earthquake represented by a number on an arbitrary scale
a magnitude six earthquake
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Merriam-Webster unabridged
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Time Traveler for magnitude
The first known use of magnitude was in the 15th century
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