Elucidation: An independent continuant that contains no  material entities as parts. Immaterial entities divide  into two major subgroups: (1) boundaries and sites, which  bound, or are demarcated in relation to, material entities,  and which can thus change location, shape, and size as their  material hosts move or change shape or size; (2) spatial  regions, which exist independently of material entities,  and which thus do not change. 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_0000141