Type genus
In biological classification
Biological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....

, a type genus is a representative genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, as with regard to a biological family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

. The term and concept is used much more often and much more formally in zoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...

 than it is in botany
Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...

, and the definition is dependent on the nomenclatural Code
Nomenclature Codes
Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic nomenclature, each in their own broad field of organisms...

 that applies:
  • In zoological nomenclature
    International Code of Zoological Nomenclature
    The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...

    , a type genus is "The nominal genus that is the name-bearing type
    Name-bearing type
    Under the International Code of Zoological Nomenclature , the name-bearing type is the biological type that determines the application of a name. Each taxon regulated by the Code at least potentially has a name-bearing type. The name-bearing type can be either a type genus , type species , or type...

     of a nominal family-group taxon."

  • In botanical nomenclature
    Botanical nomenclature
    Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature then provides names for the results of this process. The starting point for modern botanical...

    , the phrase "type genus" is used, unofficially, as a term of convenience. In the ICBN this phrase has no status. Although the code also uses type specimens for ranks up to family (all ranks must bear the name of the genus in which their types are placed), but does not refer to the genus containing that type as a "Type genus". Names above the rank of family are not under any nomenclatural restriction according to the ICBN, except where it comes to their endings.

Example: "Poa
Poa is a genus of about 500 species of grasses, native to the temperate regions of both hemispheres. Common names include meadow-grass , bluegrass , tussock , and speargrass. "Poa" is Greek for fodder...

is the type genus of the family Poaceae
The Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...

" is another way of saying that the family name Poaceae is based on the generic name Poa.
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