奠基石,基础
cornerstone n 1: the fundamental assumptions from which something is begun or developed or calculated or explained; "the whole argument rested on a basis of conjecture" [syn: {basis}, {base}, {foundation}, {fundament}, {groundwork}] 2: a stone in the exterior of a large and important building; usually carved with a date and laid with appropriate ceremonies 3: a stone at the outer corner of two intersecting masonry walls