Immunity means protection from something harmful, especially disease or punishment. Your immune system gives you immunity to illnesses you've already had: once you've recovered from chickenpox, your body remembers how to fight it off, so you probably won't get it again. Vaccines work by training your immune system to recognize diseases before you ever catch them, giving you immunity without having to get sick first.

The word also describes legal protection from consequences. Diplomats from other countries have diplomatic immunity, meaning they can't be arrested or prosecuted in the country where they work. Sometimes prosecutors offer criminals immunity from punishment in exchange for testifying against more dangerous criminals: the smaller fish goes free to help catch the bigger one.

In both cases, immunity creates a shield. Your body's immunity shields you from germs, while legal immunity shields someone from prosecution. When something has immunity, whether a person or even an idea, it's protected from attack or harm that would affect others.