Which prefix means 'against'?

• A. Ante
• B. Anti
• C. Arthr(o)
• D. Arterio

Answer: (B)

Anti- is the prefix that means against. It signals opposition or counteraction, and in medical terms it describes something that fights or counteracts a condition or pathogen. For example, antibiotics combat bacteria, antiemetics prevent vomiting, and antivirals target viruses.

Ante- means before or prior in time, as in antepartum. Arthro- denotes joints, as in arthritis. Arterio- refers to arteries, as in arteriosclerosis. So anti- best fits the meaning “against.”