mag/magna

great, large, important

Spelled mag, magna · magnus 'great, large'

Latin magnus meant great: magnify makes something larger, magnitude measures greatness, and a magnate is a person of importance.

Words built from it

magnify — to make something look larger
magn (great) + -ify (make)
magnificent — strikingly grand or impressive
magn (great) + fic (make) + -ent
magnitude — the size or importance of something
magn (great) + -itude (state of)
magnate — a powerful, wealthy person in business
magn (great) + -ate (one who)
magnanimous — generous, especially toward a rival
magn (great) + anim (spirit)
magniloquent — speaking in a grand, showy way
magn (great) + loqu (speak)

magnet — It comes from Magnesia, a region in Greece where lodestone was found, not from Latin magnus meaning great.
magazine — from Arabic makhazin 'storehouses,' not Latin magnus 'great'