Which prefix means away from?

• A. a-
• B. ab-
• C. ad-
• D. bi-

Answer: (B)

Movement direction in medical terms is shown by prefixes. The prefix ab- means away from, off, or separating, coming from Latin. It shows movement or relation away from a reference point, as in abduct, which describes moving a limb away from the midline of the body, or abduction—the act of moving away. That makes ab- the best fit for “away from.” In contrast, ad- means toward or to (as in adduction, moving toward the midline), a- often means without or lacking (not a directional cue in this context), and bi- means two.