the basis or groundwork of anything

the moral foundation of both society and religion.

the natural or prepared ground or base on which some structure rests.

the lowest division of a building, wall, or the like, usually of masonry and partly or wholly below the surface of the ground.

the act of founding, setting up, establishing, etc.

a policy in effect since the foundation.

the state of being founded.

an institution financed by a donation or legacy to aid research, education, the arts, etc.

the Ford Foundation.

an endowment for such an institution.

a cosmetic, as a cream or liquid, used as a base for facial makeup.

foundation garment.

Solitaire . a card of given denomination on which other cards are to be added according to denomination or suit.

adjective

basal , basic , fundamental , original , primary , underlying