Zoa

Zoa is a term used in different scientific contexts. In biology, zoa comes from the Greek zōa meaning “animal” and is used as a suffix in the names of animal groups, rather than as a standalone taxonomic unit. Historically, Protozoa and Metazoa referred to single-celled and multicellular animals, respectively. Protozoa traditionally grouped unicellular, animal-like eukaryotes, while Metazoa encompassed all multicellular animals. In modern taxonomy, Protozoa is often treated as a loosely defined group rather than a formal clade, and many scientists prefer to classify these organisms within broader groups such as the SAR supergroup or other eukaryotic clades. Metazoa remains a functional term for multicellular animals, within broader groupings such as Opisthokonta or Holozoa in some classifications. The term zoa is also seen in older or alternative names such as Zoophyta, used historically for “animal-like” organisms including corals and sponges, but these terms have largely been superseded by more precise clades.

In astronomy, ZOA stands for the Zone of Avoidance, a region of the sky near the plane of the Milky Way where interstellar dust and stars obstruct observations at optical wavelengths. Surveys at infrared and radio wavelengths help to reveal galaxies in the Zone of Avoidance and improve measurements of large-scale structure.