## Definition of magnitude

**:**great size or extent

- cannot wage a war of such magnitude
- —A. N. Whitehead

- the magnitude of an earthquake

**:**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

**:**a number representing the intrinsic (see intrinsic 1a) or apparent brightness of a celestial (see

^{1}celestial 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

**:**a numerical quantitative measure expressed usually as a multiple of a standard unit

**:**the intensity of an earthquake represented by a number on an arbitrary scale

- a magnitude six earthquake