From school, “domain” is the scope of all possible inputs to a function and “range” is the scope of all possible outputs.
A guitar amp has a domain of 0 to 10[^a] dialed in on the knob, and the range is the audio level, going from silent to the loudest it gets.
Domain and range are also used in Protege to describe valid classes that can comprise the “from” and “to” ends of a given type of relationship.
In Ontology
In the formal representation of ontologies, Domain is the set of classes that can fill the “from” end of an arrow linking two entities, and Range is the set of all classes (or Data Types, in the case of Datatype Properties) that can fill the “to” end of the arrow.
The Turtle syntax for asserting domain and range:
:ownsDog rdfs:domain :Human ;
rdfs:range :Dog .or.
:hasAge rdfs:domain :Person ;
rdfs:range xsd:nonNegativeInteger .