Official Definition (according to the Magisterium)
“Dogma” is a truth revealed by God, which has been definitively and authoritatively defined as such by the Magisterium of the Church, and which must be accepted by all the faithful with divine and Catholic faith (fides divina et catholica).
(cf. First Vatican Council, Dei Filius, Chap. 3; CCC 88–90; CIC can. 750 §1)
Dogmas are not theological opinions, but infallible doctrinal statements based on Sacred Scripture and apostolic tradition. They provide clarity, certainty, and unity to the faith—and protect it from error and relativization.