Iso-: Equal, like, or similar. Iso- is much used in medicine and science as, for example, in isotonic solution (a solution that has the same salt concentration as cells and blood), isotope (a form of a chemical element with the same atomic number as another element but having a different atomic mass), isocellular (composed of cells of the same size and type), and isochromosome (a chromosome with two identical equal arms). The opposite of iso- is aniso-. Iso- is derived from the Greek "isos" meaning "equal or like."
