In biological classification, family (Latin: familia, plural familiae) is a taxonomic rank. Exact details of formal nomenclature depend on the Nomenclature Code which applies.
Family, as a rank intermediate between order and genus, is a relatively recent invention.
The term familial was coined by French botanist Pierre Magnol in his Prodromus historiae generalis plantarum, in quo familiae plantarum per tabulas disponuntur (1689) where he called families (familiae) the seventy-six groups of plants he recognised in his tables. The concept of rank at that time was still in statu nascendi, and in the preface to the Prodromus Magnol spoke of uniting his families into larger genera, which is far from how the term is used today.
Since the beginning of the 20th century, however, the term has been consistently used in its modern sense. Its usage and characteristic ending of the names belonging to this category are defined in the Codes of botanical and zoological nomenclature.
Almost all families are named for a type genus, and are formed by adding the ending -idae (animals) or -aceae (plants) to the stem of the genus name. Exceptions are: