This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.
Q: Passage: Mary is referred to by the Eastern Orthodox Church, Oriental Orthodoxy, the Anglican Church, and all Eastern Catholic Churches as Theotokos, a title recognized at the Third Ecumenical Council (held at Ephesus to address the teachings of Nestorius, in 431). Theotokos (and its Latin equivalents, "Deipara" and "Dei genetrix") literally means "Godbearer". The equivalent phrase "Mater Dei" (Mother of God) is more common in Latin and so also in the other languages used in the Western Catholic Church, but this same phrase in Greek (Μήτηρ Θεοῦ), in the abbreviated form of the first and last letter of the two words (ΜΡ ΘΥ), is the indication attached to her image in Byzantine icons. The Council stated that the Church Fathers "did not hesitate to speak of the holy Virgin as the Mother of God". Question: What does the phrase "Mater Dei" mean?
A: 
Mother of God