Active immunity refers to the protection gained when the immune system is stimulated by a foreign substance like a virus or bacteria. There are various synonyms for this term, including acquired immunity, adaptive immunity, antigen-specific immunity, and specific immunity. These synonyms all refer to the same phenomenon of the immune system developing a response to a specific pathogen. Active immunity is long-lasting and provides protection against future infections by the same pathogen. This type of immunity is different from passive immunity, which is temporary and acquired from another source like a mother's breast milk or a serum injection. Understanding the various synonyms for active immunity helps scientists and healthcare professionals communicate effectively about immune system responses and vaccine development.