Catechism of the Catholic Church §461 — excerpt
Taking up St. John's expression, "The Word became flesh", The Church calls "Incarnation" the fact that the Son of God assumed a human nature in order to accomplish our salvation in it.
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.