magnitude (Noun) — The property of relative size or extent (whether large or small). ex. "they tried to predict the magnitude of the explosion" ex. "about the magnitude of a small pea"
magnitude (Noun) — A number assigned to the ratio of two quantities; two quantities are of the same order of magnitude if one is less than 10 times as large as the other; the number of magnitudes that the quantities differ is specified to within a power of 10.
magnitude (Noun) — Relative importance. ex. "a problem of the first magnitude"
magnitude (Noun) — (astronomy) the brightness of a star or other object, measured on a logarithmic scale where smaller numbers represent brighter objects; a difference of 5 magnitudes corresponds to a factor of 100 in intensity.