What does the prefix "Endo-" signify?

The prefix "endo-" signifies "within" or "inside." It is often used in medical terminology to describe structures or conditions that occur internally. For example, in the term "endoscope," it refers to an instrument designed to examine the interior of a hollow organ or body cavity. Similarly, "endocardium" refers to the inner lining of the heart. Understanding this prefix is crucial in the medical field as it helps in identifying and describing procedures, anatomical structures, or diseases that involve inner aspects of the body. This insight aligns well with the correct answer, emphasizing the significance of the prefix in conveying the concept of being inside or within something.