Substructure

n.	1.	(Arch.) Same as Substruction.
	2.	An under structure; a foundation; groundwork.

Noun	1.	substructure - the basic structure or features of a system or organization Synonyms: infrastructure
	2.	substructure - lowest support of a structure; "it was built on a base of solid rock"; "he stood at the foot of the tower" Synonyms: understructure, groundwork, base, fundament, foundation, foot

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, terra firma, underbuilding, undercarriage, undergirding, underpinning, understruction, understructure