Which of the following best defines the meaning of the root 'xen(o)'?

• A. Stranger
• B. Alien
• C. Foreign
• D. External

Answer: (D)

Xen(o) signals foreign origin rather than just being on the outside. It comes from the Greek xenos, meaning foreign, strange, or guest. In medical terms, this root is used to describe something coming from a different source or origin, not something simply located externally. That makes “foreign” the best match among the options, with “stranger” being a close everyday sense but less precise for glossary usage. “Alien” is another near meaning but not the standard term used in forming medical terms, and “external” would come from a different root (extern-), not xen-. Examples: xenograft (tissue from a different species), xenobiotic (a foreign chemical).