In biology, the family is a systematic unit and a taxonomic category located between the order and the genus; or between the superfamily and the subfamily if they were described.
As with other levels (categories) in the taxonomy of living beings, and due to the need to highlight certain common traits and kinship relationships, several families can be grouped into superfamilies, and the constituents of a family can be divided into subfamilies (and these in turn in infrafamilies).
The family is the most important taxonomic category after the genus and species. The exact details of the formal nomenclature depend on the "Codes of Nomenclature": manuals that establish the rules by which the biological nomenclature is governed.
The name of a family is made up of a radical and an ending. To name a family taxon, the radical used corresponds to the genitive of the name of the type genus of the family, not the most representative (in number of species or popularity of the name). Thus, from the genus Homo, whose genitive is hominis, whose radical is homin-, the name of the family Hominidae is derived; it is incorrect to form the family name from the radical of the nominative (Hom-o → "Homidae").
For the ending, which is what identifies the taxon to the family rank, it varies according to the different groups of organisms and the taxonomic level:
In botany the Latin ending of the superfamily is -acea.
In zoology the Latin ending of the superfamily is -oidea and in Spanish -oideas (word always plural), like Hominoidea, hominoids.
In botany the Latin ending of the family is -aceae, and in Spanish -áceas (for example Asteraceae, asteraceae). For some important families there are older traditional names that do not end like this, but are still cited more or less frequently along with the more recent names associated with a type genus. For example, Compositae (compositae) is a synonym for what is now better called Asteraceae; other notable examples are the Gramineae (Poaceae), the Leguminosae (Fabaceae), the Umbelliferae (Apiaceae) or the Guttiferae (Hypericaceae). In zoology the Latin ending of the family is -idae, and in Spanish -idos ( word always esdrújula and plural, like Felidae, felids).
In botany the Latin ending of the subfamily is -oideae (like Asteroideae, asteroideos).
In zoology the Latin ending of the subfamily is -inae and in Spanish -inos (always flat and plural word, like Homininae, hominins).
History of the concept
Family is a word of Latin origin (plural: familiae) from where it is taken for use in the scientific nomenclature of organisms.
The concept of family as a taxonomic category is a relatively recent invention. In botany, the term family was coined by the French botanist Pierre Magnol in his Prodromus historiae generalis plantarum, in quo familiae plantarum per tabulas disponuntur of 1689. There, he names as families (familiae) 76 groups of plants that he recognized in his tables . The concept of category at that time was still in its infancy, and thus the preface to the Prodromus speaks of uniting its families into larger genera, which is far from the present use of the term.
Carlos Linnaeus used the word "family" in his Philosophia Botanica (1751) to refer to larger groups of plants: trees, plants, ferns, palms, etc. He used this term only in the morphological section of the book, discussing plant organs. Subsequently, in French botanical publications, from Michel Adanson (Familles naturelles des plantes, 1763) to the end of the 19th century, the French word famille was used with