Theotokos (Θεοτόκος, translit. Theotókos) is a title of Mary, the mother of Jesus used especially in the Eastern Orthodox, Oriental Orthodox, and Eastern Catholic Churches. Its literal English translations include God-bearer and the one who gives birth to God; less literal translations include Mother of God; it is tranliterated Theotocus. The Council of Ephesus decreed in 431, that Mary is Theotokos because her son Jesus is one person who is both God and man, divine and human.
In many traditions, Theotokos was translated from the Greek into the local liturgical language. The most prominent of these are Latin (Deipara, Dei genetrix and, as paraphrased, Mater Dei), Church Slavonic (Богородица translit. Bogoroditsa), Coptic ( translit. Ti.Theotokós), Arabic (والدة الله translit. Wālidat Allah), Georgian (ღვთისმშობელი translit. Ghvtismshobeli), Armenian: (Աստվածամայր translit.Astvatzamayr or Աստվածածին translit.Astvadzatzin), and Romanian (Născătoare de Dumnezeu or Maica Domnului).
The main use of the English term Mother of God has been, and still is, as an imprecise translation of Theotokos that frequently requires explanation. The other principal use of Mother of God has been as the precise and literal translation of Μήτηρ Θεού, a Greek term which has an established usage of its own in traditional Christian theological writing, hymnography, and iconography. In an abbreviated form ΜΡ ΘΥ it often is found on Orthodox icons (see illustration above), where it is used to identify Mary.
A hymn normally sung as part of the Greek Divine Liturgy includes both titles in close proximity, in both cases referring to Mary, showing that the titles are not synonymous: "It is truly fitting to call you blessed, the Theotokos, ever-blessed and wholly pure and the Mother of our God (Ἄξιόν ἐστιν ὡς ἀληθῶς μακαρίζειν σὲ τὴν Θεοτόκον, τὴν ἀειμακάριστον καὶ παναμώμητον καὶ μητέρα του Θεοῦ ἡμῶν...", emphasis added.) The difference between the two terms is that the former, Theotokos explicitly refers to physical childbearing, while the latter, Mother of God, describes a family relationship but not necessarily physical childbearing. Within the Christian tradition, Mother of God has not been understood, or intended to be understood, as referring to Mary as Mother of God from eternity, that is, as Mother of God the Father, but only with reference to the birth of Jesus, that is, the Incarnation; but this limitation in the meaning of Mother of God must be understood by the person employing the term. By contrast, Theotokos makes it explicit, thus excluding any misunderstanding of Mary's divine maternity.
However, those reading or hearing the English phrase Mother of God as a translation of a Greek text cannot — unless they know the Greek text in question, or obtain additional information — know whether the phrase is a literal translation of Μήτηρ Θεού or an imprecise rendering of Θεοτόκος or one its Latin equivalents or equivalents in other languages.
The term Mother of God is justified by Catholic and Orthodox Christians by in which Elizabeth greets the Virgin Mary as the "mother of my Lord."
On the other hand, Christians believe God the Son is begotten of God the Father "from all eternity" (see Trinity and Nicene Creed), but is born "in time" of Mary. Theotokos thus refers to the Incarnation, when the Second Person of the Holy Trinity took on human nature in addition to his pre-existing divine nature, this being made possible through the cooperation of Mary.
Since mainstream Christians understand Jesus Christ as both fully God and fully human, they call Mary Theotokos to affirm the fullness of God's incarnation. The Council of Ephesus decreed, in opposition to those who denied Mary the title Theotokos ("the one who gives birth to God") but called her Christotokos ("the one who gives birth to Christ"), that Mary is Theotokos because her son Jesus is one person who is both God and man, divine and human. As Cyril of Alexandria wrote, "I am amazed that there are some who are entirely in doubt as to whether the holy Virgin should be called Theotokos or not. For if our Lord Jesus Christ is God, how is the holy Virgin who gave [Him] birth, not [Theotokos]?" (Epistle 1, to the monks of Egypt; PG 77:13B). Thus the significance of Theotokos lies more in what it says about Jesus than any declaration about Mary.
Within the Orthodox doctrinal teaching on the economy of salvation, Mary's identity, role, and status as Theotokos is acknowledged as indispensable, and is for this reason formally defined as official dogma. The only other Mariological teaching so defined is that of her virginity. Both of these teachings have a bearing on the identity of Jesus Christ. By contrast, certain other Marian beliefs which do not bear directly on the doctrine concerning the person of Jesus (for example, her sinlessness, the circumstances surrounding her conception and birth, her Presentation in the Temple, her continuing virginity following the birth of Jesus, and her death), which are taught and believed by the Orthodox Church (being expressed in the Church's liturgy and patristic writings), are nonetheless not formally defined by the Church, and belief in them is not a precondition for baptism.
Origen (d. 254) is often cited as the earliest author to use Theotokos for Mary (Socrates, Ecclesiastical History 7.32 citing Origen's Commentary on Romans) but the text upon which this assertion is based may not be genuine.
Nestorius' opponents, led by Cyril of Alexandria, viewed this as dividing Jesus into two distinct persons, the human who was Son of Mary, and the divine who was not. To them, this was unacceptable since by destroying the perfect union of the divine and human natures in Christ, it sabotaged the fullness of the Incarnation and, by extension, the salvation of humanity. The council accepted Cyril's reasoning, affirmed the title Theotokos for Mary, and anathematised Nestorius' view as heresy. (See Nestorianism)
In letters to Nestorius which were afterwards included among the council documents, Cyril explained his doctrine. He noted that "the holy fathers... have ventured to call the holy Virgin [T]heotokos, not as though the nature of the [W]ord or his divinity received the beginning of their existence from the holy Virgin, but because from her was born his holy body, rationally endowed with a soul, with which [body] the [W]ord was united according to the hypostasis, and is said to have been begotten according to the flesh" (Cyril's second letter to Nestorius).
Explaining his rejection of Nestorius' preferred title for Mary (Christotokos), Cyril wrote: "Confessing the Word to be united with the flesh according to the hypostasis, we worship one Son and Lord, Jesus Christ. We do not divide him into parts and separate man and God as though they were united with each other [only] through a unity of dignity and authority... nor do we name separately Christ the Word from God, and in similar fashion, separately, another Christ from the woman, but we know only one Christ, the Word from God the Father with his own flesh... But we do not say that the Word from God dwelt as in an ordinary human born of the holy virgin... we understand that, when he became flesh, not in the same way as he is said to dwell among the saints do we distinguish the manner of the indwelling; but he was united by nature and not turned into flesh... There is, then, one Christ and Son and Lord, not with the sort of conjunction that a human being might have with God as in a unity of dignity or authority; for equality of honor does not unite natures. For Peter and John were equal to each other in honor, both of them being apostles and holy disciples, but the two were not one. Nor do we understand the manner of conjunction to be one of juxtaposition, for this is insufficient in regard to natural union.... Rather we reject the term 'conjunction' as being inadequate to express the union... [T]he holy virgin gave birth in the flesh to God united with the flesh according to hypostasis, for that reason we call her Theotokos... If anyone does not confess that Emmanuel is, in truth, God, and therefore that the holy virgin is Theotokos (for she bore in a fleshly manner the Word from God become flesh), let him be anathema." (Cyril's third letter to Nestorius)
By the end of his life, Nestorius had agreed to the title Theotokos, stating the apparent communication of the attributes (idiomata).
Other examples include Beneath thy compassion dating from the third century, the Hail Mary in its Eastern form, and All creation rejoices, which replaces Axion Estin at the Divine Liturgy on the Sundays of Great Lent.