Which prefix means middle?

• A. Medi/o
• B. Iatr/o
• C. Psych/o
• D. Stomat/o

Answer: (A)

The prefix meaning middle is medi/o. It comes from Latin medius, meaning middle, and it appears in terms that describe something toward the midline of the body, like mediastinum (the central area in the chest between the lungs) and medial (toward the midline). The other prefixes don’t convey middle: iatr/o relates to healing or medical treatment, psych/o to the mind, and stomat/o to the mouth. So medi/o is the correct combining form for “middle.”