magnitude
Pluralmagnitudes
- 1The size, extent, or importance of something, considered on its own or in comparison with other things.
Engineers struggled to grasp the full magnitude of the damage to the bridge.
The magnitude of the financial loss forced the company to close several offices.
Similarextent, scale, size, scope, enormity
Note
The sense closest to the Latin root: magnitūdō meant "greatness, size" and was built on magnus, "great." Every technical meaning on the page narrows this one into a number. In everyday prose it often follows a demonstrative, as in works of this magnitude or a crisis of that magnitude, where it signals scale and seriousness at once. It can be uncountable (the sheer magnitude) or countable when sizes are compared.
- 2A factor of roughly ten in size or quantity, used to express how much larger or smaller one thing is than another.
The two populations differ by three magnitudes, a thousandfold gap.
Storage capacity grew by a magnitude within just a few years.
- 3A number expressing the energy released by an earthquake, such as on the Richter scale, with higher values indicating stronger quakes.
The quake's magnitude was revised upward after analysts reviewed the seismic data.
A magnitude above eight can trigger destructive tsunamis along nearby coasts.
Note
Seismologists use the word for the energy released by a quake, which is a single figure for the event itself. Unlike the stargazer's scale, higher numbers mean stronger quakes. The Richter scale is the best-known example but not the only one, so a precise report names the scale it uses. In news writing the word often stands before the number as a label, as in a magnitude-7 earthquake.
- 4A measure of how bright a star appears from Earth, with lower values indicating brighter objects.
Sirius has a magnitude of about minus one, making it the brightest star in the night sky.
Faint galaxies have a magnitude too high for the naked eye to detect.
Note
Astronomy's brightness scale runs backward: the smaller the number, the brighter the star, and the most brilliant objects fall below zero. The scale is logarithmic, built so that a gap of five magnitudes means one object looks a hundred times brighter than the other. The full term is apparent magnitude, which describes brightness as it reaches an observer rather than a fixed property of the star.
- 5A number assigned to something so that it can be compared numerically with others.
The algorithm ranks data points by magnitude before grouping them.
Two readings with the same magnitude are treated as equal in the model.
Similarvalue
Note
In mathematics the word names the act of reduction: whatever the thing is, its magnitude is the single figure that lets it be ranked against others. The idea is deliberately general. The length of a vector is one familiar instance, and in that case the measurement has to be specified carefully.
- 6The norm of a vector, most often the Euclidean two-norm, representing the vector's overall length.
The magnitude of a vector equals the square root of the sum of its squared components.
In physics, speed is simply the magnitude of the velocity vector.
Note
A vector has both a direction and a size, and here the word picks out the size alone, a scalar that ignores which way the vector points. The phrase "most commonly" matters. The default is the Euclidean two-norm, but other norms measure length differently, so careful technical writing states which norm is meant whenever the choice is not obvious.
- 7A logarithmic measure expressing a ratio of intensities, used in astronomy to compare brightness on a fixed scale.
A difference of five magnitudes corresponds to a hundredfold change in brightness.
The catalog lists a magnitude for every object it records.
Note
Here the word becomes a countable unit, so magnitudes can be added up like degrees. It measures dimming as readily as brightness. Andreas Eckart and his co-authors write in 2005 of "~25–30 magnitudes of extinction" blocking visible light toward the Milky Way's center. The logarithmic scale is the one behind a star's apparent brightness, applied here to differences of intensity rather than to a single star.
Practice
Can you tell the meanings of magnitude apart? Answer 3 quick questions from this page, or write your own sentence and AI will check it.
Origin
From Latin magnitūdō ("greatness, size"), formed from magnus ("great") and the suffix -tūdō.