An Etymological Dictionary of Astronomy and Astrophysics

A measure of brightness in astronomy on a → logarithmic scale in which a difference of five magnitudes represents a difference of 100 times in brightness. In this scale the lower a magnitude, the brighter the object. The faintest magnitude reached by → unaided eye is 6.

Etymology (EN): From L. magnitudo “greatness, bulk, size,” from magnus “great,” cognate with Pers. meh “great, large” (Mid.Pers. meh, mas; Av. maz-, masan-, mazant- “great, important,” mazan- “greatness, majesty,” mazišta- “greatest;” cf. Skt. mah-, mahant-; Gk. megas; PIE *meg- “great”) + -tudo, suffix forming abstract nouns from adjectives and participles.

Etymology (PE): Borz “height, magnitude” (it occurs also in the name of the mountain chain Alborz), related to boland “high,” bâlâ “up, above, high, elevated, height,” berg “mountain, hill” (Mid.Pers. buland “high;” O.Pers. baršan- “height;” Av. barəz- “high, mount,” barezan- “height;” cf. Skt. bhrant- “high;” L. fortis “strong” (Fr. & E. force); O.E. burg, burh “castle, fortified place,” from P.Gmc. *burgs “fortress;” Ger. Burg “castle,” Goth. baurgs “city,” E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg); PIE base *bhergh- “high”). Qadr, from Ar.