Note that this can refer to a material entity like an organ or muscle, or an immaterial entity (a site or fiat boundary) like skin, stomach cavity or lung surface.
Note that this can refer to a material entity like an organ or muscle, or an immaterial entity (a site or fiat boundary) like skin, stomach cavity or lung surface.
b is a site means: b 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. (axiom label in BFO2 Reference: [034-002])