Moneran is a term that refers to a group of unicellular microorganisms that lack nuclei, organelles, and a cell membrane. These simple organisms are often classified as bacteria, but they differ in terms of structure and behavior. Some synonyms for the term moneran include prokaryote, microbial organism, microbe, and protobiont. Prokaryotes are single-celled organisms that do not have a true nucleus, and they are categorized into two groups, bacteria and archaea. Microbial organism is a broad term that refers to any living organism that can only be seen with a microscope. Microbe refers to any microscopic organism, including bacteria, archaea, viruses, fungi, and protozoa. Protobiont refers to an early evolutionary stage of life that existed before the emergence of cells with nuclei.