| Term | Definition |
| in a modern taxonomic system, a domain made up of prokaryotes that usually have a cell wall and that reproduce by cell division; this domain aligns with the traditional kingdom Eubacteria | Bacteria |
| in a modern taxonomic system, a domain made up of prokaryotes that can live in extreme environments and that are differentiated from other prokaryotes by various important chemical differences; this domain aligns with the kingdom Archaebacteria | Archaea |
| in a modern taxonomic system, a domain made up of all eukaryotes; aligns with the traditional kingdoms Protista, Fungi, Plantae, and Animalia | Eukarya |
| in a traditional taxonomic system, a kingdom that contains all prokaryotes except Kingdom Archaebacteria (Domain Archaea); biologists more recently prefer to classify these organisms as Domain Bacteria | Eubacteria |
| in a traditional taxonomic system, a kingdom made up of prokaryotes that can live in extreme environments; differentiated from other prokaryotes by various important chemical differences; biologists more recently prefer to classify them as Domain Archaea | Archaebacteria |
| in a traditional taxonomic system, a kingdom made up of mostly one-celled eukaryotic organisms that are not readily classified as either plants, animals, or fungi | Protista |
| in a traditional taxonomic system, a kingdom made up on nongreen, eukaryotic organisms that get food by breaking down organic matter and absorbing the nutrients, reproduce by means of spores, and have no means of movement | Fungi |
| in a taxonomic system, a kingdom made up of eukaryotic, multicellular organisms that have cell walls made mostly of cellulose, that have pigments that absorb light, & that supply energy & oxygen to themselves & to other life-forms through photosynthesis | Plantae |
| in a traditional taxonomic system, a kingdom made up of complex, multicellular organisms that lack cell walls, are usually able to move around, and possess specialized sense organs that help them quickly respond to their environment | Animalia |
