Elucidation: An immaterial entity in which objects such as molecules of air or organisms can be contained. 'S' is a site means: 'S' is a three-dimensional immaterial entity that is (partially or wholly) bounded by a material entity or it is a three-dimensional immaterial part thereof. Example of usage: a hole in the interior of a portion of cheese; an air traffic control region defined in the airspace above an airport; a rabbit hole; your left nostril (a fiat part – the opening – of your left nasal cavity); the interior of a kangaroo pouch; the hold of a ship; the lumen of your gut; the interior of your bedroom. Source: Robert Arp, Barry Smith, and Andrew D. Spear: Building Ontologies with Basic Formal Ontology. The MIT Press Cambridge, Massachusetts London, England. ©2015 Massachusetts Institute of Technology. ISBN 978-0-262-52781-1, Glossary. https://www.ebi.ac.uk/ols4/ontologies/bfo/classes/http%253A%252F%252Fpurl.obolibrary.org%252Fobo%252FBFO_0000029