The millet system was the framework the Ottoman Empire used to govern its many religious communities, granting each recognized millet, Greek Orthodox, Armenian Apostolic, Jewish and eventually others, legal authority over its own members' family law, education and internal religious affairs, while the imperial government retained control of taxation, military service and matters touching the state as a whole.
The system traces informally to 1454, when Sultan Mehmed II recognized the Greek Orthodox Patriarch of Constantinople as the civil and religious head of the empire's Orthodox Christian subjects shortly after the conquest of the city, though the formal structure and the term "millet" itself developed gradually over the following centuries rather than arriving fully formed on that date.
The arrangement let a vast, religiously diverse empire govern itself without forcing conversion or cultural uniformity on its subject peoples, at the cost of treating religious identity as the primary basis of legal status rather than a private matter. The system dissolved with the empire itself in the early twentieth century, as the secular Turkish republic that succeeded it under Mustafa Kemal Ataturk replaced millet based law with a single civil code applied equally to all citizens.