What is the definition of apostasy according to the Catholic Church?

I always thought apostasy meant denying the divinity of Jesus Christ and becoming an atheist, Jew, Muslim, Hindu, etc. However today at Mass the priest in his homily mentioned how one of his parishioner’s nephew went from being a Catholic to a minister at an evangelical church. The priest said this was apostasy because he left Catholicism. I thought leaving the Church, but remaining Christian just meant a person would go into schism or at worse heresy, but not apostasy since they still believe Jesus is divine. What does the Catholic Church define as apostasy? Thank you.

From the Catechism (broken up and bold for clarity):

2089 Incredulity is the neglect of revealed truth or the willful refusal to assent to it. "**Heresy **is the obstinate post-baptismal denial of some truth which must be believed with divine and catholic faith, or it is likewise an obstinate doubt concerning the same;

**apostasy **is the total repudiation of the Christian faith;

**schism **is the refusal of submission to the Roman Pontiff or of communion with the members of the Church subject to him."

You are correct that the individual in question is in schism from the Catholic Church and since he has become a Protestant minister he is therefore in heresy.

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