We defend the fundamental ontological-pragmatic principle that where there are continua in reality science is often forced to make partly fiat terminological delimitations. In particular, this principle applies when it comes to describing biological organisms, their parts, properties, and relations. Human-made fiat delimitations are indispensable at the level of both individuals and the natural kinds which they instantiate. The kinds of pragmatically based ‘fiatness’ that we describe can create incompatibilities and lack of interoperability even between properly designed ontologies, if not (...) appropriately handled. (shrink)