Definition of the Union of the Divine and Human Natures in the Person of Christ

Council of Chalcedon, 451 ad, Act v.

HEREFORE, following the holy fathers,
we all with one accord teach men to acknowledge one and the same Son, our Lord Jesus Christ,
At once complete in Godhead and complete in manhood, truly God and truly man, consisting also of a reasonable soul and body;
Of one substance (homoousios) with the Father as regards his Godhead,
    and at the same time of one substance with us as regards his manhood;
    like us in all things apart from sin;
As regards his Godhead, begotten of the Father before the ages,
    but yet as regards his manhood, begotten
    for us men and for our salvation of Mary the virgin, the God-bearer (Theotokos);
One and the same Christ, Son, Lord, Only-begotten,
    made known in two natures, without confusion, without change, without division, without separation;
The distinction of natures being in no way annulled by the union,
    but rather the property of each nature being preserved
    and coming together to form one person (prosopon) and subsistence (hypostasis),
Not as parted or separated into two persons (prosopa),
    but one and the same Son and Only-begotten, God the Word (Logos), Lord Jesus Christ;
Even as the prophets from earliest times spoke of him,
    and our Lord Jesus Christ himself tutored us,
    and the council of the fathers has handed down to us.