Other forms: magnitudes
Magnitude is size stated rather than felt — how big something is, put as a number or a place on a scale. An earthquake of magnitude 6.2. The magnitude of the debt, once somebody added the invoices up.
In everyday use it means sheer scale and it takes of: the magnitude of the problem, the magnitude of the task ahead. Science makes it exact. Earthquake magnitude runs on a logarithmic scale, so a 7 releases far more energy than a 6, not a little more. Astronomers use magnitude for how bright a star looks, and that scale runs backwards — the lower the number, the brighter the star. In maths, the magnitude of a vector is its size with the direction stripped away. And an order of magnitude is a factor of ten, so two orders of magnitude bigger means a hundred times bigger, not merely a lot.
1nounextentThe great size or importance of something.
“Nobody had grasped the magnitude of the task until the first week ended.”
formal in this meaning — an editor’s judgement
2nounmagnitudeA number on a scale showing the strength of an earthquake.
“The quake had a magnitude of 6.8 and was felt two hundred miles away.”
3nounbrightA number showing how bright a star appears, where a lower number means a brighter star.
“Sirius shines at a magnitude of about minus one and a half.”
4nounquantityThe size of a quantity in mathematics or physics, taken without its direction.
“A vector has a magnitude and a direction, and you need both.”
magnitude is a measure of size.
Magnitude is Latin magnitūdō, greatness or size, built on magnus, great — the same magnus that swells through magnify and magnificent. English took the Latin word almost whole and handed it to the sciences, which needed a word for bigness that could carry a number.
Latin
magnitūdō — greatness, size
English, today
magnitude
From Latin magnitūdō (“greatness, size”), magnus + tūdō.
Etymology from Wiktionary, CC BY-SA
Practised in Science & Space, Academic English