Order (biology)

In biological classification, the order (Latin: ordo) is

  1. a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. The well-known ranks in descending order are: life, domain, kingdom, phylum, class, order, family, genus, and species, with order fitting in between class and family. An immediately higher rank, superorder, is sometimes added directly above order, with suborder directly beneath order.
  2. a taxonomic unit (a taxon; plural taxa) in the rank of order (e.g. Strigiformes, Rosales). In that case the plural is orders (Latin ordines).
DomainKingdomClassOrderFamily
The hierarchy of biological classification's eight major taxonomic ranks. A class contains one or more orders. Intermediate minor rankings are not shown.

What does and does not belong to each order is determined by a taxonomist, as is whether a particular order should be recognized at all. Often there is no exact agreement, with different taxonomists each taking a different position. There are no hard rules that a taxonomist needs to follow in describing or recognizing an order. Some taxa are accepted almost universally, while others are recognized only rarely.[1]

The name of an order is usually written with a capital letter.[2] For some groups of organisms, their orders may follow consistent naming schemes. Orders of plants, fungi, and algae use the suffix -ales (e.g. Dictyotales).[3] Orders of birds and fishes use the Latin suffix -(i)formes meaning 'having the form of' (e.g. Passeriformes), but orders of mammals and invertebrates are not so consistent (e.g. Artiodactyla, Actiniaria, Primates).


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