What does metazoan mean?
Metazoan means “multicellular animal” and is used in biology to distinguish animals whose bodies consist of multiple cells from organisms traditionally described as single-celled protozoans. The word can function as a noun for an individual multicellular animal, but it is also commonly used collectively, as in the study of metazoan evolution or metazoan diversity. It is chiefly a scientific term rather than a general synonym for “animal,” because everyday speech rarely needs to make this distinction. In formal zoological usage, metazoans belong to the group Metazoa, whose members possess differentiated cells and, in most cases, tissues. Researchers invoke the term when discussing animal body plans, evolutionary transitions, fossils, and relationships among animal groups. Its specialized character makes it especially useful in zoology, evolutionary biology, paleontology, parasitology, and biological education.
Any multicellular animal, especially a member of the taxonomic group Metazoa.
"The fossil is among the oldest known metazoans."
Used chiefly in scientific and educational contexts; often discussed collectively rather than for one individual organism.
Of or relating to multicellular animals or the taxonomic group Metazoa.
"Researchers compared metazoan body plans across several fossil groups."
A formal, primarily scientific adjective.
Used when referring to multiple multicellular animals as distinct individuals or taxonomic subjects.
"The museum displays fossils of several metazoans that lived in the ancient sea."
The word metazoan literally means “after animal”: as zoology came to distinguish single-celled protozoans from animals with multiple cells, it used this name for the multicellular majority.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does metazoan come from?
Metazoan was formed in the 19th century from Greek meta-, meaning “after,” and zōion, meaning “animal.” The construction reflects the historical contrast between single-celled protozoans and multicellular animals. The same Greek element underlies words including zoology, zoologist, zoomorphic, and zoon.
How metazoan is actually used
The noun is mainly used in zoology, biology, paleontology, and related technical writing. The adjective is scholarly and is less common in general prose. In modern classification, Metazoa excludes sponges and comprises the animals treated as Eumetazoa in some traditional schemes.
Easily confused with metazoan
A metazoan is multicellular, whereas the term protozoan traditionally refers to a single-celled organism viewed as an animal.