- ordered ranking of levels where each level contains or governs the one below
- biological taxonomy: domain, kingdom, phylum, class, order, family, genus, species
- organizational: executive, management, operational layers
- protocol layers: OSI model (physical, data link, network, transport, session, presentation, application)
- file systems: root, directories, subdirectories, files
- Maslow’s hierarchy of needs: physiological, safety, belonging, esteem, self-actualization
- Chomsky hierarchy: regular, context-free, context-sensitive, recursively enumerable languages
- holarchy: each level is both a whole and a part of a larger whole (Arthur Koestler’s holon)
- hierarchies enable modularity, abstraction, and scalable organization