1. A period of isolation or separation from others in order to control the spread of an infectious disease: "For many centuries, quarantines were one of the few available means for halting the spread of infectious diseases."

"A quarantine means that a person, or people, will have to stay in isolation separated from others and avoid contact with anyone else."

2. Etymology: derived from the Latin quadraginta, "forty". Originally, this referred to the amount of time a widow could remain in her deceased husband’s house, then it referred to the period of time a ship had to wait off a country’s port if its passengers were stricken with a disease. Now, a quarantine can mean a period of isolation for any length of time.

The meaning of "period a ship suspected of carrying disease is kept in isolation" is from Italian quarantina giorni; literally, "a space of forty days" from quaranta, "forty". The term comes from the Venetian custom of keeping ships that came from plague-stricken countries from entering its port for a period of 40 days.

To keep someone, or groups of people, or an animal, or animals in obligatory or enforced separation or isolation from others as a sanitary precaution to prevent the spread of a contagious disease: "A river cruise boat had a hundred passengers on board and forty of them came down with an intestinal-viral infection and were taken to hospitals while the others were quarantined aboard the boat and not allowed to leave."

"Martin's dog became very ill and the veteranarian immediately quarantined her."