Which of the following prefixes means "within"?

The prefix that means "within" is "endo-". This prefix is derived from the Greek word "endon," which translates to "inside" or "within." In medical terminology, it is commonly used in terms such as "endoscopy," which refers to a procedure that involves looking inside the body, often through a flexible tube. Another example is "endocrine," which pertains to glands that release hormones into the bloodstream from within the body.

Understanding the meaning of this prefix is crucial for interpreting various medical terms, particularly those related to anatomy and procedures that involve internal structures. The other prefixes, while they have their specific meanings, do not convey the idea of "within" like "endo-" does.