Is "grave sin" the same thing as "mortal sin"?

Canon 916 of The Code of Canon Law states:

Can. 916 A person who is conscious of grave sin is not to celebrate Mass or receive the body of the Lord without previous sacramental confession unless there is a grave reason and there is no opportunity to confess; in this case the person is to remember the obligation to make an act of perfect contrition which includes the resolution of confessing as soon as possible.

Is the reference to “grave sin” talking about mortal sin? What is confusing to me is that they are not the same, since mortal sin also needs two other conditions (full knowledge, and full consent). What I have always thought is that if you are in a state of mortal sin without having gone to confession then you should not receive The Holy Eucharist.

Now, in the Catechism no. 2352, in reference to a grave sin, it says that due to conditions like “force of acquired habit”, etc., a person can lessen their moral responsibility even to a minimum (grave sin but not meeting the condition of full consent for it to be mortal).

2352… To form an equitable judgment about the subjects’ moral responsibility and to guide pastoral action, one must take into account the affective immaturity, force of acquired habit, conditions of anxiety, or other psychological or social factors that can lessen, if not even reduce to a minimum, moral culpability.

If Canon 916 is not referencing mortal sin, but merely grave sin, whether mortal or not, then I do not need to discern whether my sin is mortal in respect to receiving The Holy Eucharist, but simply whether it is grave sin. Making that distinction, in a case of grave sin that is not believed to me mortal sin, the only thing I should really be discerning before receiving Communion at mass is whether I had a grave reason for not getting to confession, or if I did not have the opportunity, and then of course resolve to going to confession ASAP assuming that I felt I had achieved an act of perfect contrition. The inability to go to confession does not even seem remotely possible anyway considering the abundance of Catholic churches near me and the range of mass times from Saturday night to Sunday night.

Do I understand this correctly? Thanks in advance.

“Grave sin” (as quoted from canon law) is synonymous with “mortal sin” (as quoted from the catechism). Sin involving grave matter but lacking full knowledge and/or complete consent is not grave sin, it is venial sin.

The Catechism explains, “One commits venial sin when, in a less serious matter, he does not observe the standard prescribed by the moral law, or when he disobeys the moral law in a grave matter, but without full knowledge or without complete consent” (Catechism, 1862).

Canon 916 concerns mortal sin only, not venial.

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