An ontology is a controlled vocabulary that describes a domain in the form of a graph, where entities in the graph are connected by named relationships. An ontology can be thought of like a supercharged [[taxonomy]], or a series of connected taxonomies. Where a taxonomy has a limited number of relationships (usually parent/child, or broader/narrower), an ontology can have many kinds of relationships, and the relationships can be as descriptive as needed.  Image: *Florian Thiery, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons*