What does "exo-" mean when used as a prefix?

The prefix "exo-" originates from Greek and means "outside" or "outward." When it is used in medical terminology or other scientific contexts, it generally indicates something that is external or situated on the outside of a structure. For example, in the term "exoskeleton," it refers to the external skeleton found in arthropods and some other organisms.

Understanding the meaning of this prefix can help in grasping various terms across different fields of study, especially in biology and anatomy, where distinguishing between internal and external aspects is crucial. The other prefixes mentioned pertain to different concepts: "inside" refers to internal structures, "normal" typically relates to standard or typical conditions, and "half" denotes a divided state. Each term serves distinct purposes, but "exo-" specifically denotes an outward or external position.