反:Prefix generally meaning "against, opposite or opposing, and contrary."Inmedicine, anti- often connotes "counteracting or effective against" as inantibacterial,anti-infective, andantiviral. Sometimes medical terms containing anti- take on new meanings as has occurred with抗生素andantibody. As a prefix, anti- may be shortened to ant- as in antacid. "Anti" is the Greek word for "against."
