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| Kingdom | in the Linnaean taxonomic system, the highest taxonomic classification into which organisms are grouped, based on fundamental similarities and common ancestry. The Linnaean system designates five such classifications: animals, plants, fungi, prokaryotes, and protoctists |
| Phylum | the primary subdivision of a taxonomic kingdom, grouping together all classes of organisms that have the same body plan |
| Class | a taxonomic category ranking below a phylum or division and above an order |
| Order | the usual major subdivision of a class or subclass in the classification of organisms, consisting of several families |
| Family | the usual major subdivision of an order or suborder in the classification of plants, animals, fungi, etc., usually consisting of several genera |
| Genus | the usual major subdivision of a family or subfamily in the classification of organisms, usually consisting of more than one species |
| Species | the major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but are not able to breed with members of another species |
| Binomial nomenclature | the scientific system of naming an organism using two terms, the first being the genus and the second the species |
| Monera | a taxonomic kingdom of prokaryotic organisms that typically reproduce by asexual budding or fission and have a nutritional mode of absorption, photosynthesis, or chemosynthesis, comprising the bacteria, blue-green algae, and various primitive pathogens |
| Protista | eukaryotic one-celled living organisms distinct from multicellular plants and animals: protozoa, slime molds, and eukaryotic algae |
| Fungi | a taxonomic kingdom, or in some classification schemes a division of the kingdom Plantae, comprising all the fungus groups and sometimes also the slime molds |
| Plantae | the taxonomic kingdom comprising all living or extinct plants |
| Animalia | taxonomic kingdom comprising all living or extinct animals |
| Archaebacteria | a group of microorganisms, including the methanogens and certain halophiles and thermoacidophiles, that have RNA sequences, coenzymes, and a cell wall composition that are different from all other organisms: considered to be an ancient form of life that evolved separately from the bacteria and blue-green algae and sometimes classified as a kingdom |
| Eubacteria | spherical or rod-shaped bacteria of the order Eubacteriales, characterized by simple, undifferentiated cells with rigid walls; true bacteria |
