strain

A taxon is any unit used in the science of biological classification, known as taxonomy. Taxa are organized in a hierarchy, from kingdom down to subspecies. For example, in the classification of animals, recognized categories include kingdom, phylum, class, order, family, genus, species, and subspecies.1

A strain is a specific subtype within a biological species that possesses distinct genetic variations. This term is often used for genetically controlled variants within a species, particularly in domestic animals where a true-breeding, genetically pure line is called a strain. In botany, a similar concept is referred to as a cultivar.21