Which prefix means backwards?

• A. Trip-
• B. Gen-
• C. Epi-
• D. Retr(o)-

Answer: (D)

The concept being tested is how prefixes convey direction in medical terms. The prefix retr(o)- (the combining form of retro-) means backward or behind. It shows up in terms like retroflex (bending backward) or retrograde (moving backward along a path). Because retro- indicates behind or backward, retr(o)- carries the same meaning when attached to a root. The other options don’t express backward direction: trip-/tri- means three; gen- relates to origin or kind; epi- means upon or above. So retr(o)- is the one that conveys backwards.