The notion in graph theory that corresponds to induced substructures is that of induced subgraphs. Universal algebra studies the lattice of substructures of a structure in detail. The closed subsets (or induced substructures) of a structure form a lattice. For structures with relations there are notions of weak and of induced substructures. These substructures have different morphology and functions. This and other analogous injective functions from substructures are sometimes called natural injections. They are usually found as substructures of more complex molecules ("substituted aromatics"). This leads to dampness in substructures such as crawlspaces and basements. Its focus is on the structure of the family, including its various substructures. Such optimal substructures are usually described by means of recursion. The following are equivalent characterizations of Archimedean fields in terms of these substructures. Databases enabling such searching of chemical substructures are indispensable. In addition to coupling of substructures, one is also able to decouple substructures from assemblies. The paving is supported by massive arched substructures, which extend under the surrounding houses. In this sense, society itself, and most of its substructures, are complex sociotechnical systems.