Order (taxonomy)

{{short description|Taxonomic rank between class and family}} {{About|the taxonomic rank|other uses|Order (disambiguation){{!}}Order}} {{Biological classification}} {{Use dmy dates|date=April 2026}} '''Order''' ({{langx|la|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.<ref>{{cite book |last1=Tobin |first1=Allan J. |last2=Dusheck |first2=Jennie |title=Asking About Life |year=2005 |publisher=Cengage Learning |place=Boston |isbn=978-0-030-27044-4 |pages=403–408 |url=https://books.google.com/books?id=cjgdW4SjoJcC}}</ref>

The name of an order is usually written with a capital letter.<ref>{{cite web |author=Translation Bureau |date=15 October 2015 |title=Capitalization: Biological Terms |url=https://www.btb.termiumplus.gc.ca/tpv2guides/guides/wrtps/index-eng.html?lang=eng&lettr=indx_catlog_c&page=9sjs7LoC_fRo.html |access-date=19 June 2020 |website=Writing Tips, TERMIUM Plus® |publisher=Public Services & Procurement Canada}}</ref> For some groups of organisms, their orders may follow consistent naming schemes. Orders of plants, fungi, and algae use the suffix {{lang|la|-ales}} (e.g. Dictyotales).<ref>{{harvnb|McNeill et al. 2012|Article 17.1|ref= McNeill}}</ref> Orders of birds and fishes<ref name = Berg1940>{{cite book |author=Leo S. Berg |author-link=Lev Berg |title=Classification of fishes, both recent and fossil |year=1940 |lang=ru, en |publisher=J. N. Edwards |location=Ann Arbor Michigan |url=https://ia601404.us.archive.org/25/items/in.ernet.dli.2015.19051/2015.19051.Classification-Of-Fishes-Both-Recent-And-Fossil_text.pdf}}</ref> use the Latin suffix {{lang|la|-iformes}} meaning 'having the form of' (e.g. Passeriformes), most orders of insects use the suffix {{lang|grc|-ptera}} meaning 'wing', but orders of mammals, reptiles, amphibians and invertebrates are not so consistent (e.g. Artiodactyla, Anura, Crocodylia, Actiniaria, Primates).

==Hierarchy of ranks== ===Zoology=== For some clades covered by the International Code of Zoological Nomenclature, several additional classifications are sometimes used, although not all of these are officially recognized.

{| class="wikitable sortable" |+ |- ! Name !! Latin prefix !! Examples |- | Magnorder || ''magnus'', 'large, great, important' || Boreoeutheria, Atlantogenata |- | Superorder || ''super'', 'above' || Euarchontoglires, Laurasiatheria, Afrotheria |- | Grandorder || ''grandis'', 'large' || Euarchonta, Ferungulata |- | Mirorder || ''mirus'', 'wonderful, strange' || Primatomorpha, Ferae, Euungulata |- | Order || || Primates, Procolophonomorpha, Carnivora, Artiodactyla, Pilosa |- | Suborder || ''sub'', 'under' || Haplorrhini, Procolophonia, Whippomorpha, Vermilingua |- | Infraorder || ''infra'', 'below' || Simiiformes, Tarsiiformes, Cetacea |- | Parvorder || ''parvus'', 'small, unimportant' || Catarrhini, Odontoceti, Mysticeti |}

In their 1997 classification of mammals, McKenna and Bell used two extra levels between superorder and order: ''grandorder'' and ''mirorder''.<ref name="McKennaBell1997">{{Citation |last1=McKenna |first1=M.C. |last2=Bell |first2=S.G. |year=1997 |title=Classification of Mammals |location=New York |publisher=Columbia University Press |isbn=978-0-231-11013-6 |name-list-style=amp}}</ref> Michael Novacek (1986) inserted them at the same position. Michael Benton (2005) inserted them between superorder and magnorder instead.<ref name="MichaelJBenton2005_VPalaentology_3rd">{{cite book |last=Benton |first=Michael J. |year=2005 |title=Vertebrate Palaeontology |edition=3rd |place=Oxford |publisher=Blackwell Publishing |isbn=978-0-63205-637-8}}</ref> This position was adopted by ''Systema Naturae 2000'' and others.

===Botany=== In botany, the ranks of subclass and suborder are secondary ranks pre-defined as respectively above and below the rank of order.<ref name=botarticle4>{{harvnb|McNeill et al. 2012|Article 4|ref= McNeill}}</ref> Any number of further ranks can be used as long as they are clearly defined.<ref name=botarticle4/>

The superorder rank is commonly used, with the ending {{lang|la|-anae}} that was initiated by Armen Takhtajan's publications from 1966 onwards.<ref>{{citation |last=Naik |first=V.N. |year=1984 |title=Taxonomy of Angiosperms |publisher=Tata McGraw-Hill |isbn=9780074517888 |url=https://books.google.com/books?id=GanmtXAyU0gC |page=111}}</ref>

==History== The order as a distinct rank of biological classification having its own distinctive name (and not just called a ''higher genus'' ({{lang|la|genus summum}})) was first introduced by the German botanist Augustus Quirinus Rivinus in his classification of plants that appeared in a series of treatises in the 1690s. Carl Linnaeus was the first to apply it consistently to the division of all three kingdoms of nature (then minerals, plants, and animals) in his ''Systema Naturae'' (1735, 1st. Ed.).

===Botany=== [[File:Linnaeus1758-title-page.jpg|thumb|right|Title page of the 1758 edition of Linnaeus's ''Systema Naturæ''.<ref name=Linn1758>{{cite book |last=Linnaeus |first=Carolus |title=Systema naturae per regna tria naturae :secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis |publisher=Laurentius Salvius |location=Stockholm |year=1758 |url=https://www.biodiversitylibrary.org/bibliography/542 |language=la |edition=10th}}</ref>]] For plants, Linnaeus' orders in the ''Systema Naturae'' and the ''Species Plantarum'' were strictly artificial, introduced to subdivide the artificial classes into more comprehensible smaller groups. When the word {{lang|la|ordo}} was first consistently used for natural units of plants, in 19th-century works such as the ''Prodromus Systematis Naturalis Regni Vegetabilis'' of Augustin Pyramus de Candolle and the ''Genera Plantarum'' of Bentham & Hooker, it indicated taxa that are now given the rank of family (see ordo naturalis, '''natural order''<nowiki/>').

In French botanical publications, from Michel Adanson's {{lang|fr|Familles naturelles des plantes}} (1763) and until the end of the 19th century, the word {{lang|fr|famille}} (plural: {{lang|fr|familles}}) was used as a French equivalent for this Latin {{lang|la|ordo}}. This equivalence was explicitly stated in the {{lang|fr|italics=unset|Alphonse Pyramus de Candolle}}'s {{lang|fr|Lois de la nomenclature botanique}} (1868), the precursor of the currently used ''International Code of Nomenclature for algae, fungi, and plants''.

In the first international ''Rules'' of botanical nomenclature from the International Botanical Congress of 1905, the word ''family'' ({{lang|la|familia}}) was assigned to the rank indicated by the French {{lang|fr|famille}}, while order ({{lang|la|ordo}}) was reserved for a higher rank, for what in the 19th century had often been named a 'cohort' ({{lang|la|cohors}},<ref>{{cite book |author=Briquet, J. |year=1912 |title=Règles internationales de la nomenclature botanique adoptées par le congrès international de botanique de Vienne 1905, deuxième edition mise au point d'après les décisions du congrès international de botanique de Bruxelles 1910; International rules of botanical nomenclature adopted by the International Botanical Congresses of Vienna 1905 and Brussels 1910; Internationale Regeln der botanischen Nomenclatur angenommen von den Internationalen Botanischen Kongressen zu Wien 1905 und Brüssel 1910 |publisher=Gustav Fischer |location=Jena |url=https://archive.org/details/rglesinternati00inteuoft}} Page 1.</ref> plural {{lang|la|cohortes}}).

Some of the plant families still retain the names of Linnaean "natural orders" or even the names of pre-Linnaean natural groups recognized by Linnaeus as orders in his natural classification (e.g. ''Palmae'' or ''Labiatae''). Such names are known as descriptive family names.

===Zoology=== In the field of zoology, the Linnaean orders were used more consistently. That is, the orders in the zoology part of the ''Systema Naturae'' refer to natural groups. Some of his ordinal names are still in use, e.g. Lepidoptera (moths and butterflies) and Diptera (flies, mosquitoes, midges, and gnats).<ref name="General2">{{cite book |author=Carl von Linné, translated by William Turton |year=1806 |title=Volume 2: Insects |series=A general system of nature: through the three grand kingdoms of animals, vegetables, and minerals, systematically divided into their several classes, orders, genera, species, and varieties |publisher=Lackington, Allen, and Co |location=London |url=https://books.google.com/books?id=pgQuAAAAYAAJ}}</ref>

===Virology=== From 1991 to 2017, order was the highest rank used to classify viruses in a system that ranged from order to species. In 2018, the International Committee on Taxonomy of Viruses, which oversees virus taxonomy, added ranks higher than order up to the highest taxonomic rank of realm. Virus orders are indicated by the suffix -''virales''.<ref>{{cite journal |author=International Committee on Taxonomy of Viruses Executive Committee |date=May 2020 |title=The New Scope of Virus Taxonomy: Partitioning the Virosphere Into 15 Hierarchical Ranks |journal=Nat Microbiol |volume=5 |issue=5 |pages=668–674 |doi=10.1038/s41564-020-0709-x |pmc=7186216 |pmid=32341570}}</ref><ref>{{cite web |date=March 2025 |title=The International Code of Virus Classification and Nomenclature (ICVCN; the ICTV Code) |url=https://ictv.global/about/code |publisher=International Committee on Taxonomy of Viruses |access-date=15 September 2025}}</ref>

==References== {{Reflist}}

==Works cited== * {{cite book |author1=McNeill, J. |author2=Barrie, F.R. |author3=Buck, W.R. |author4=Demoulin, V. |author5=Greuter, W. |author6=Hawksworth, D.L. |author7=Herendeen, P.S. |author8=Knapp, S. |author9=Marhold, K. |author10=Prado, J. |author11=Prud'homme Van Reine, W.F. |author12=Smith, G.F. |author13=Wiersema, J.H. |author14=Turland, N.J. |year=2012 |series=Regnum Vegetabile |volume=154 |title=International Code of Nomenclature for algae, fungi, and plants (Melbourne Code) adopted by the Eighteenth International Botanical Congress Melbourne, Australia, July 2011 |publisher=A.R.G. Gantner Verlag KG |isbn=978-3-87429-425-6 |url=http://www.iapt-taxon.org/nomen/main.php?page=title |ref=McNeill}}

Category:Orders (biology) Category:Botanical nomenclature Category:Plant taxonomy rank08 Category:Bacterial nomenclature Category:Taxonomic ranks