In the field of information science ontology is a term used as a formal representation of a set of concepts and relationships between them within a domain. The term 'ontology' originally comes from philosophy and represents a concept that deals with the study of being or existence.
However, unlike controlled vocabularies, ontologies have more complex relationships between the terms than controlled vocabularies. One of these relationships are inferences that define set of rules to determine what additional facts can be implied if other facts are known.
For instance, in explaining relationships between people, relationships between children and parents have inverse relations: a person can be a parent to a child, but not the other way around.
Ontologies especially find their purpose in Artificial Intelligence (AI) where they are utilized for creating computational models that enable automated reasoning. They are also extensively used in biomedical research, genetics, and geographic information systems among others.
Ontologies have their purpose in the process of FAIRification by defining the semantic model.