a combining form appearing in loanwords from Latin, where it meant “large,” “great”: magnify.

Also especially before a vowel, magn-.

Origin of magni-

< Latin, combining form of magnus Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Word Origin and History for magni-

word-forming element meaning "great," from Latin magni-, comb. form of magnus "great" (see magnate (n.)).

Online Etymology Dictionary, © 2010 Douglas Harper