In taxonomy

Taxonomy

Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

, circumscription is the definition of the limits of a taxonomic group of organisms. One goal of taxonomy is to achieve a stable circumscription for every taxonomic group. Achieving stability can be simple or difficult.

An example of a taxonomic group with unstable circumscription is Anacardiaceae

Anacardiaceae

Anacardiaceae are a family of flowering plants bearing fruits that are drupes and in some cases producing urushiol, an irritant. Anacardiaceae include numerous genera with several of economic importance. Notable plants in this family include cashew , mango, poison ivy, sumac, smoke tree, and marula...

, a 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...

 of flowering plant

Flowering plant

The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...

s. Some experts favor a circumscription in which this family includes the subfamilies Cassuvieae, Spodiaceae, and Spondiaceae (which other experts segregate into other families, namely Cassuviaceae, Spodiadaceae, and Spondiadaceae), and excludes the segregate families Blepharocaryaceae, Julianaceae, Pistaciaceae, and Podoaceae.

See also

• Circumscription (logic)
• Circumscriptional name
  Circumscriptional name
  Circumscriptional names are taxon names used above family-group level that are not ruled by ICZN and are defined by the particular set of members included, not the number of species....
  
  
• Circumscribed circle
  Circumscribed circle
  In geometry, the circumscribed circle or circumcircle of a polygon is a circle which passes through all the vertices of the polygon. The center of this circle is called the circumcenter....
  
  
• Venn diagram
  Venn diagram
  Venn diagrams or set diagrams are diagrams that show all possible logical relations between a finite collection of sets . Venn diagrams were conceived around 1880 by John Venn...