A digital compilation combining a thesaurus with inference rules, designed to structure information systematically. It outlines concepts within a domain, defining terms and their interrelations, thus enabling both humans and machines to interpret complex data. Ontologies support a variety of applications, from semantic web services to knowledge management, by providing a clear framework for the organization and retrieval of knowledge. This structured knowledge representation is crucial for enhancing data interoperability, enabling advanced search capabilities, and facilitating decision-making processes in artificial intelligence systems.