Final answer:
The term that describes the body's ability to resist invaders and the diseases they cause is immunity, particularly active immunity, which involves memory lymphocytes like B or T cells.
Step-by-step explanation:
The term for the body's ability to resist invaders and the diseases they cause is immunity. Immunity involves the formation of memory lymphocytes, such as B or T cells, which enable the body to respond quickly and effectively to pathogens it has previously encountered. This adaptive immune response results in active immunity, which is the type of immunity acquired when memory lymphocytes are produced after exposure to a pathogen, often through infection or vaccination. There are also other types of immunity like passive immunity, which occurs when a person receives antibodies from another source, rather than producing them through their own immune system.