Ontology in artificial intelligence is a structured framework for organizing information within a specific domain. It comprises a set of concepts, categories, and relationships that define how different entities relate to one another. Ontologies are used to create a common vocabulary, facilitating better communication and understanding among systems, applications, and users. They play a vital role in knowledge representation, semantic web technologies, and natural language processing by enabling machines to understand and reason about the information more effectively. Ontologies help enhance data interoperability, making it easier to integrate diverse datasets and improve the accuracy of AI applications, such as information retrieval and question answering.