groundwork

(noun) the fundamental assumptions from which something is begun or developed or calculated or explained. Synonyms: basis, base, foundation, fundament, cornerstone. Examples: "The whole argument rested on a basis of conjecture."

(noun) lowest support of a structure. Synonyms: foundation, base, fundament, foot, substructure, understructure. Examples: "It was built on a base of solid rock." "He stood at the foot of the tower."

(noun) preliminary preparation as a basis or foundation. Examples: "We are prepared today because of groundwork that was done ten years ago."