Catechism of the Catholic Church §209 — excerpt
Out of respect for the holiness of God, the people of Israel do not pronounce his name. In the reading of Sacred Scripture, the revealed name (YHWH) is replaced by the divine title "LORD" (in Hebrew Adonai, in Greek Kyrios).
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.