Q.Define the terms immunity and immune system.

Immunity = the body's capacity to resist pathogens; the immune system = the network of cells, tissues and organs that provides that defence.

These two closely-related terms from the Immune System / Human Health and Disease topic of NCERT Class 12 Biology are defined as:

• Immunity: the ability of the host (body) to fight against and protect itself from disease-causing organisms (pathogens) and their toxins, as well as other foreign (non-self) substances. It may be innate (present from birth) or acquired (developed after exposure). …