If you contract something highly infectious, such as pinkeye, please quarantine yourself so that you don’t infect others with it. This means you’ll have to stay in isolation and avoid contact with other people.
Starting in the 16th century, a quarantine lasted specifically 40 days. The word is in fact derived from the Latin quadraginta, which means "forty." Originally, this referred to the amount of time a widow could remain in her deceased husband’s house, then referred to the period of time a ship had to wait off a country’s port if its passengers were disease-stricken. Now, it can mean a period of isolation of any length, and can be used as both a verb and a noun.