Educational Content: This article is for informational purposes only and does not constitute medical advice. Always consult a healthcare provider for diagnosis and treatment.
Definition of Anti
Medically reviewed by Min Clinic Staff | Updated: January 2026
Anti-: Prefix generally meaning "against, opposite or opposing, and contrary." In medicine, anti- often connotes "counteracting or effective against" as in antibacterial, anti-infective, and antiviral. Sometimes medical terms containing anti- take on new meanings as has occurred with antibiotic and antibody. As a prefix, anti- may be shortened to ant- as in antacid. "Anti" is the Greek word for "against."