Order (taxonomy)

Order (Latin: ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. Like the other ranks, orders reflect shared ancestry; for example, all owls belong to the order Strigiformes. In biological classification systems, orders and their usage are defined by nomenclature codes. An immediately higher rank, superorder, is sometimes added directly above order, with suborder directly beneath order.

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.

The name of an order is usually written with a capital letter. 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). Orders of birds and fishes use the Latin suffix -iformes meaning 'having the form of' (e.g. Passeriformes), most orders of insects use the suffix -ptera meaning 'wing', but orders of mammals, reptiles, amphibians and invertebrates are not so consistent (e.g. Artiodactyla, Anura, Crocodylia, Actiniaria, Primates).