The phrase "sub strata" is most often used to refer to the underlying layers or levels of a particular system, structure or organization. Synonyms for this term include substratum, foundation, groundwork, basis, bedrock, fundamental principles, underlying principles, and bottom-most layer. These words all share the same idea of being the essential support or basis upon which something is built or constructed. Other synonyms may also include support structure, core principles, underlying concepts, and fundamental beliefs. Regardless of the specific term used, the idea of the sub strata is an essential component of any well-built system or structure.