- Foundation - Sound knowledge in a subject - of Ground - The act, method, or process of laying a groundwork or
foundation; hence, elementary instruction; the act or process of
applying a ground, as of color, to wall paper, cotton cloth, etc.; a
basis.
- background - Cornerstone - Foundation - Groundwork - Headquarters is said to be a cornerstone - The foundation of anything; that on which a thing rests. - The pedestal of a column, pillar, or statue.