A floodplain is a region of relevance that has the floodplain role, i.e. for areas between surface waters and dykes or high banks and other areas that are flooded or flowed through during flooding of a surface water body or that are used for flood relief or retention.
A forest is a region of relevance that has the forest role, i.e. it is planted with forest plants as well as clear-cut or thinned ground areas, forest paths, forest division and safety strips, forest openings and clearings, forest meadows, game grazing areas, wood storage areas and other areas connected to and serving the forest.
A subregion is a region of relevance that is in every respect a component of a region of relevance, but never encompasses the entire extent of a region of relevance.
BFO 2 Reference: Spatial regions do not participate in processes.
Editor note:
Spatial region doesn't have a closure axiom because the subclasses don't exhaust all possibilites. An example would be the union of a spatial point and a spatial line that doesn't overlap the point, or two spatial lines that intersect at a single point. In both cases the resultant spatial region is neither 0-dimensional, 1-dimensional, 2-dimensional, or 3-dimensional.
Ontology