What prefix signifies 'excessive,' 'over,' or 'many'?

The prefix that signifies 'excessive,' 'over,' or 'many' is hyper-. This prefix is commonly used in medical terminology to indicate a condition characterized by an excess or exaggeration. For instance, the term "hypertension" refers to excessive blood pressure.

While "multi-" indicates many or multiple and is used in terms such as "multivitamin," it does not carry the connotation of excess as hyper- does. "Poly-" also suggests many, as seen in "polyuria," which refers to excessive urination, but it does not universally denote excess in a general sense. "Mega-" implies something large or great but does not specifically mean excess in a quantitative way.

Therefore, hyper- is the most accurate prefix to describe an excessive characteristic in medical terminology.