What prefix means outside or external?

The prefix that means outside or external is "Exo-." This prefix is derived from the Greek word "exo," which means "outside" or "outer." It is commonly used in various scientific and medical terminology to indicate something that is located outside of a certain structure or system. For instance, in the term "exoskeleton," it refers to a hard outer structure that provides support and protection to an organism.

Other prefixes listed have different meanings: "Dia-" usually means through or across, "Peri-" relates to surrounding or encircling, and "Endo-" signifies something that is within or inside. Understanding the meanings of these prefixes can enhance the comprehension of medical terminology and its application in various fields.