under or below an object or a surface; at a lower place or level; directly beneath; "we could see the original painting underneath"; "a house with a good foundation underneath"
on the lower or downward side; on the underside of; "a chest of drawers all scratched underneath"
any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes; "a diet high in protein"