Terminology:

Theotokos "God-bearer", "Mother of God"

Aiparthenos "ever-virgin"

Panagia "all holy"

Dormition "passage through death"

Assumption "ascension into heaven"

The name "Theotokos" was made official by the III Ecumenical Council (Ephesus, 431 AD) which decreed that the Virgin should be honored by this name which confirms the Orthodox belief in the Incarnation: that Christ was both true God and true man. As so often happened in those days, this action was a response to heretical teachings that needed to be addressed. Thus, once and for all, the Church affirmed her teachings about Christ and Theotokos.