Which prefix is used to indicate "within" in medical terms?

The prefix "intra-" is used to indicate "within" in medical terminology. This prefix comes from Latin, where "intra" means "inside" or "within." In medical contexts, it is commonly used to describe structures, conditions, or procedures that occur inside a particular organ or system. For instance, "intravenous" refers to something administered within a vein, emphasizing that the action takes place inside the vascular system.

Understanding prefixes in medical terms is crucial for interpreting a wide range of medical vocabulary. While other prefixes like "inter-" often mean "between," "extra-" means "outside," and "sub-" refers to "under" or "below," it is "intra-" that specifically conveys an inner or internal relationship, making it the correct choice for indicating "within."