Eastern Church:
- one or more of the non-Roman catholic churches
- one or more of the Eastern Erthodox communion churches
- The Byzantine and Antiochene (Syriac) Rite Churches (catholic, orthodox, and/or Nestorian)
- some admixutre of the above
The understanding of the Eucharist is the same. The term Transubstatiation is particularly Catholic, but the actual understanding it embodies is shared amongst the Catholic, Eastern Orthodox, Nestorian, and Oriental Churches.
Most of the EO accept the Assumption vis-a-vis Mary was taken to heaven bodily at the time of her death. Whether or not she was still in her body is another matter.
The Immaculate conception is trickier. Some do, some donāt, and many donāt understand why it is even an issue. Suffice it to say that Mary is held in higher esteem than any other saint (including the Archangels) by the ECās and the EO. Sheās commemorated more than any other mortal in the Liturgy of St. John and of St. Basil.
This may help, itās from the Ruthenian Catholic usage of the DL of St. John: āIt is truly proper to Glorify you, Oh Theotokos, the ever blessed, immaculate, and the Mother of our God. More honorable than the cherubim, and beyond compare, more glorious than the seraphim, who a virgin gave birth to God the Word, you truly the Theotokos, we magnifyā (Theotokos = God-Birther). It is called the Theotokion, the hymn to the God-birther. The orthodox ones are very similar, differing in various translations.
Hereās the one from Orthodox Wiki:
āIt is truly right to bless you, O Theotokos, ever blessed, and most pure, and the Mother of our God: more honorable than the cherubim, beyond compare more glorious than the seraphim ā without corruption you gave birth to God, the Word. True Theotokos, we magnify you!ā
orthodoxwiki.org/Troparion#Theotokion
The Theotokion is sung at almost every divine liturgy of St John and of St Basil. It is also sung during vespers and matins. In any case, alternate wordings are used on specific feasts.