What does the prefix ab- mean?

• A. Away from
• B. Toward
• C. Without
• D. To, in the direction of

Answer: (A)

This prefix signals movement away from a point of reference, usually the midline of the body. In medical terms, ab- means away from, off, or from the center. A classic example is abduction, when a limb moves away from the body’s midline; the muscle that causes this is called an abductor. This idea contrasts with ad-, which means toward or toward the midline, as in adduction. For “without,” prefixes like a- or an- are used, not ab-. For “to, in the direction of,” ad- is the appropriate prefix. So ab- is best understood as meaning away from.