Theotokos

Theotokos is the Greek title for Mary, the Mother of God; the literal sense is "God-bearer" or "the one who gave birth to God." The title was affirmed at the Council of Ephesus in 431 as the appropriate title for Mary in light of the Incarnation: in giving birth to Jesus Christ, who is one person with two natures (divine and human), Mary is rightly called the Mother of God. The title is used liturgically and devotionally in Orthodox and Eastern Catholic tradition particularly, in many of the principal Marian feasts and in the hymnody of the Divine Liturgy. The Latin equivalent is Mater Dei; the English "Mother of God" is the standard rendering.