Order (biology)
In scientific classification used in biology, the
order is ▪ a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family. An immediately higher rank,
superorder, may be added directly above order, while
suborder would be a lower rank. ▪ a taxonomic unit, a taxon, in that rank. In that case the plural is orders.
Example: Walnuts and hickories belong to the family Juglandaceae, which is placed in the order Fagales. What does and does not belong to each order is determined by a taxonomist. Similarly for the question if 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 recognised only rarely. For some groups of organisms, consistent suffixes are used to denote that the rank is an order.