base, basement, basis, bearing wall, bed, bedding, bedrock, bottom, floor, flooring, fond, footing, foundation, fundament, fundamental, ground, grounds, groundwork, hardpan, infrastructure, pavement, principle, radical, riprap, rock bottom, rudiment, seat, sill, solid ground, solid rock, stereobate, stylobate, substratum, substruction, substructure, terra firma, underbuilding, undercarriage, undergirding, underpinning, understruction