Which prefix would you use to denote something relating to many or multiple cells?

The prefix that denotes something relating to many or multiple cells is "poly-." This prefix comes from the Greek word "polus," meaning "many" or "much." In medical terminology, "poly" is commonly used to describe conditions or phenomena involving a large number of cells, such as "polycythemia," which refers to an increased level of red blood cells in the bloodstream.

The other prefixes have specific meanings that do not convey the idea of multiplicity as "poly-" does. For instance, "uni-" means one or single, "mono-" implies one or alone, and "bi-" signifies two. Therefore, when referring to multiple cells, "poly-" is the correct prefix to use, capturing the essence of plurality that is central to the concept.