Delineations

Species

Generally, the term means a kind or variety and can denote anything from cats to quarks. Originally from the Latin specere, meaning “to look or behold,” the word has different meanings in different fields, both in and out of science. In biology, it is the lowest full unit of the Linnaean taxonomy classification system (kingdom, phylum, class, order, genus, and species), but scientists have wrangled for years over such issues as whether a given species is capable of breeding with another. In chemistry, the term can represent either an atom, ion, fragment, element, or molecule.