Quarantine is the practice of isolating people, animals, or things that might carry disease to prevent illness from spreading. When someone has been exposed to a contagious disease, they might need to stay in quarantine for a period of time, away from others, to make sure they don't get sick or pass the illness along.

Quarantine works on a simple principle: diseases spread through contact, so separating sick people (or people who might be sick) from healthy people stops the chain of infection. A family might quarantine a new pet for a few weeks to ensure it's healthy before introducing it to other animals. Agricultural inspectors quarantine imported plants to check for invasive insects. During disease outbreaks, health officials might quarantine entire buildings, neighborhoods, or ships.

The word can also be used more casually, like when you quarantine your younger sibling's muddy shoes in the garage, or when the library quarantines returned books for a day before reshelving them.