magnitude

UK: /ˈmægnɪtjuːd/

US: /ˈmægnɪˌtud, -ˌtjud/

US: (mag′ni to̅o̅d′, -tyo̅o̅d′)

WordReference Random House Learner's Dictionary of American English © 2026

mag•ni•tude /ˈmægnɪˌtud, -ˌtyud/   n. [uncountable]

1. greatness of size or amount.
2. great importance or consequence:
   an event of great magnitude to the world.

Idioms

3. Idioms of the first magnitude, of greatest significance.

WordReference Random House Unabridged Dictionary of American English © 2026

mag•ni•tude  (mag′ni to̅o̅d′, -tyo̅o̅d′), n. 

1. size; extent;
   dimensions:
   to determine the magnitude of an angle.
2. great importance or consequence:
   affairs of magnitude.
3. greatness of size or amount.
4. moral greatness:
   magnitude of mind.
5. Astronomy
   • Also called visual magnitude, apparent magnitude. the brightness of a star or other celestial body as viewed by the unaided eye and expressed by a mathematical ratio of 2.512: a star of the first magnitude is approximately 2½ times as bright as one of the second magnitude and 100 times brighter than one of the sixth magnitude. Only stars of the sixth magnitude or brighter can be seen with the unaided eye.
   • See absolute magnitude. 
6. [Math.] a number characteristic of a quantity and forming a basis for comparison with similar quantities, as length.
7. of the first magnitude, of utmost or major importance:
   an artist of the first magnitude.

• Latin magnitūdō. See magni-, -tude
• Middle English 1350–1400

mag•ni•tu•di•nous  (mag′ni to̅o̅d′n əs, -tyo̅o̅d′-), adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

magnitude / ˈmæɡnɪˌtjuːd/ noun

1. relative importance or significance: a problem of the first magnitude
2. relative size or extent: the magnitude of the explosion
3. a number assigned to a quantity, such as weight, and used as a basis of comparison for the measurement of similar quantities
4. Also called: apparent magnitude the apparent brightness of a celestial body expressed on a numerical scale on which bright stars have a low value. Values are measured by eye (visual magnitude) or more accurately by photometric or photographic methods, and range from –26.7 (the sun), through 1.5 (Sirius), down to about +30. Each integral value represents a brightness 2.512 times greater than the next highest integral value
   See also absolute magnitude, visual magnitude
5. Also called: earthquake magnitude a measure of the size of an earthquake based on the quantity of energy released: specified on the Richter scale
   See Richter scale

Etymology: 14th Century: from Latin magnitūdō size, from magnus great