Catechism of the Catholic Church §242 — excerpt
Following this apostolic tradition, the Church confessed at the first ecumenical council at Nicaea (325) that the Son is "consubstantial" with the Father, that is, one only God with him.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: The English phrases "of one being" · "one in being" translate the Greek word homoousios, which was rendered in Latin by consubstantialis · Niceno-Constantinopolitan Creed · DS 150