Plentiful comes from Middle English plenty (from Old French plente, from Latin plenitas 'fullness', from plenus 'full') + -ful. The suffix is part of the word's derivational shape, marking the final grammatical or semantic role while the base supplies the central meaning. As an adjective, it carries the sense "existing in great quantity; abundant", with the older formation still helping explain the modern use. Relevant historical forms include Old French plente, Latin plenus, and Proto-Indo-European *pleh₁-. Derivative forms include plentifully, plentifulness; related words include plenty, plenteous, plenitude.