Definition: A taxon is Extinct when there is no reasonable doubt that the last individual has died. A
taxon is presumed Extinct when exhaustive surveys in known and/or expected habitat,
at appropriate times (diurnal, seasonal, annual), throughout its historic range have failed
to record an individual. Surveys should be over a time frame appropriate to the taxon’s
life cycle and life form.
Definition: Salts and esters of phosphoric and oligophosphoric acids and their chalcogen analogues. In inorganic chemistry, the term is also used to describe anionic coordination entities with phosphorus as central atom.