- megaVery large.
- mega-Very large, great.
- megacycliteA monoclinic-prismatic mineral containing hydrogen, oxygen, potassium, silicon, and sodium.
- megalo-large, great or exaggerated
- megalopterousRelating to or characteristic of the order Megaloptera, which comprises insects with large wings and aquatic larvae.
- megapolisA very large city or urban complex; a metropolis.
- megasporangiumA sporangium which produces only megaspores
- megathereAn extinct, gigantic, ground sloth (Megatherium americanum) that flourished in South America during the Pleistocene epoch.