The term "photoion" refers to the process of ionization of a molecule or an atom through the absorption of a photon. Some synonyms for this word include photoionization, ionization by light, photon-induced ionization, and photodetachment. Photoionization is a fundamental process in various fields such as astrophysics, chemistry, and radiation biology. In astrophysics, photoionization is used to study the properties of interstellar matter and the formation of galaxies. In radiation biology, it is used to investigate the effects of radiation on living organisms. In chemistry, it is used to understand the electronic properties of molecules and atoms. Understanding the concept of photoionization and its synonyms is essential in advancing research and technology in these various fields.