Which Creed is Which?
In one of the quirks of church history, the "Nicene Creed" used in church hymnals and liturgies is a different creed from the one accepted at Nicaea.
In 381, the council of Constantinople affirmed the Nicene Creed and condemned heresies that had since arisen against Nicaea. But from later records (preserved at the Council of Chalcedon, 70 years later) we know that another creed was also used, now known as the Niceno—Constantinopolitan Creed. This creed is more strictly Trinitarian than the Nicene, describing each member of the Trinity in relation to the other members. The creed of 325 says less about the Father and only mentions the Holy Spirit with no description at all, since the council's attention was fixed on how the Son is no less divine than the Father.
The version below is the one used in the Western church; the Eastern version does not include the phrases in brackets. In particular, the statement that the Holy Spirit proceeds from the Father "and the Son" is still contested by the Eastern Orthodox Church as an unwarranted addition to Nicene theology.
The Original Nicene Creed
We believe in one God, the Father, almighty, maker of all things visible and invisible;
And in one Lord Jesus Christ, the son of God, begotten from the Father, only-begotten, that is, from the substance of the Father, God from God, light from light, true God from true God, begotten not made, of one substance from the Father, through Whom all things came into being, things in heaven and things on earth, who because of us men and because of our salvation came down and became incarnate, becoming man, suffered and rose again on the third day, ascended to the heavens, will come to judge the living and the dead;
And in the Holy Spirit.