What is "Serious Sin"?

At RCIA this week our pastor told our candidates and catechumens that there are three categories of sin: Mortal, Venial, and Serious. Serious seemed to be somewhere in between Mortal and Venial. In 77 years as a Catholic, I have never heard of a category of sin called “Serious Sin”. Serious sin seems to involve serious matter, but not bad enough to totally destroy our relation with God, as we have always been taught is the result of Mortal Sin.

He also indicated that missing Mass on Sunday once for no good reason might be a venial sin, not a mortal sin.

Am I behind the times, or is this faulty teaching? I hate the idea of giving our new Catholics-to-be incorrect teaching. PLEASE HELP!

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Recommended Reading:

[LIST]
*]Sin
*]Mortal and Venial Sin?

*]Is missing Sunday Mass considered a mortal sin?
*]Is Missing Mass a Grave Sin?
[/LIST]

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