]> relationship contained_in C contained_in C' if and only if: given any instance c that instantiates C at a time t, there is some c' such that: c' instantiates C' at time t and c located_in c' at t, and it is not the case that c *overlaps* c' at t. (c' is a conduit or cavity.) PMID:15892874 http://sswapmeet.sswap.info/obo/owl/PMID#PMID_15892874 Containment obtains in each case between material and immaterial continuants, for instance: lung contained_in thoracic cavity; bladder contained_in pelvic cavity. Hence containment is not a transitive relation. If c part_of c1 at t then we have also, by our definition and by the axioms of mereology applied to spatial regions, c located_in c1 at t. Thus, many examples of instance-level location relations for continuants are in fact cases of instance-level parthood. For material continuants location and parthood coincide. Containment is location not involving parthood, and arises only where some immaterial continuant is involved. To understand this relation, we first define overlap for continuants as follows: c1 overlap c2 at t =def for some c, c part_of c1 at t and c part_of c2 at t. The containment relation on the instance level can then be defined (see definition):