Understructures, also known as substructures, refer to the foundation or supporting framework of a building or structure. Antonyms for this word include superstructures, which refer to the upper portion or visible part of a building, and non-structures, which are objects or materials that do not have any inherent framework or foundation. Other antonyms could include disassembled, destroyed, or deconstructed, which all indicate the opposite of a built or established foundation. The importance of having a solid understructure cannot be understated, as it is the foundation upon which all other aspects of a structure rest. Without a strong understructure, a building is vulnerable to collapse or other safety hazards.