Christian feast day: Hypatius of Bithynia (Eastern Orthodox and Byzantine Catholic Churches)

Hypatius of Bithynia was a monk and hermit of the fifth century. A Phrygian, he became a hermit at the age of nineteen in Thrace. He then traveled to Constantinople and then Chalcedon with another hermit named Jason. He became abbot of a hermitage at Chalcedon.

Eastern Orthodoxy, otherwise known as Eastern Orthodox Christianity or Byzantine Christianity, is one of the three main branches of Chalcedonian Christianity, alongside Catholicism and Protestantism. Like the Pentarchy of the first millennium, the mainstream Eastern Orthodox Church is organised into autocephalous churches independent from each other. In the 21st century, the number of mainstream autocephalous churches is seventeen; there also exist autocephalous churches unrecognized by those mainstream ones. Autocephalous churches choose their own primate. Autocephalous churches can have jurisdiction (authority) over other churches, some of which have the status of "autonomous" which means they have more autonomy than simple eparchies.

Greek Catholic Church or Byzantine-Catholic Church may refer to:

• The Catholic Church in Greece
• The Eastern Orthodox Church
• The Eastern Catholic Churches that use the Byzantine Rite, also known as the Greek Rite:
  • The Albanian Greek Catholic Church
  • The Belarusian Greek Catholic Church
  • The Bulgarian Greek Catholic Church
  • The Greek Catholic Church of Croatia and Serbia
  • The Greek Byzantine Catholic Church
  • The Hungarian Greek Catholic Church
  • The Italo-Albanian Catholic Church
  • The Macedonian Greek Catholic Church
  • The Malta Greek Catholic Church
  • The Melkite Greek Catholic Church
  • The Romanian Greek Catholic Church
  • The Russian Greek Catholic Church
  • The Ruthenian Greek Catholic Church
  • The Slovak Greek Catholic Church
  • The Ukrainian Greek Catholic Church
• Any other Eastern Catholic group that uses the Byzantine Rite:
  • The Georgian Byzantine-Rite Catholics
  • An Ordinariate for Eastern Catholic faithful