Recently I gave a talk on Mary to an RCIA group. I'll be posting parts of it over the next few days.
Mary, Mother of the Church.
For more than 2000 years Mary, the mother of Jesus, has been written about, prayed to and adored. It is important to remember we do not worship Mary, but venerate her. In Latin the term for this veneration is hyperdulia. Dulia is veneration of the saints. Hyperdulia is therefore the highest form of veneration, but does not equate to worship. The word which is equates to the worship reserved to God is Latria. So theologically we differentiate the honor due God from that due the saints, and after God the highest honor is given to Our Lady.
Mother of God (Theotokos)
Though Latin is the official language of the Latin Church, the first language of the Church was Greek. That was the language that most of the new Testament was written in. This was also the language of the Old Testament scripture used by Christ himself, the Septuagint. And this was the language of the educated theologians and Church fathers who met at Ephesus for the Third Ecumenical Council in the Year of our Lord 431. This council was called to deal with the heresy of the Nestorians. Nestorius was the Bishop of Constantinople, which was at that time the capital of the Eastern Roman Empire.
Nestorius claimed that Mary was the mother of Jesus, but not the mother of God. He also declared that only Jesus' human side suffered and died on the cross. This belief made of Jesus two different persons and denied the reality of the Incarnation.
This could not stand and so a council was called. At that council it was declared that Jesus, the Word, the second Person of the Divine Trinity was Incarnate, that is he was en-fleshed in the womb of Mary. The divine nature of the Son was united with the human nature, in one undivided person: Jesus.
Since that is so, Mary who was and is the mother of Jesus must be the Mother of God, and so she is. This belief is held to this day by the Orthodox and Catholic Churches and even some Protestant groups. In Greek the word for "Mother of God" is Theotokos.