Yes! Grave matter is a prerequisite for mortal sin, but it is not the only one, as has been said. You cannot say that it is a mortal sin without more information about the specific circumstance. You can say that it is objectively sinful, and a sin of grave matter. It could be a mortal sin, but you cannot usually know unless it is your own sin. You can say with certainty that one of the three conditions for mortal sin has been met: it is indeed grave matter.
The Catechism, the Canon, the Catholic Encyclopedia, and even in Catholic Answers tracts, use the term *mortal sin *most often in the objective context. It is most often used when there is the connotation that all the conditions are met. If the conditions weren’t met then the term *mortal sin *would not apply and therefore not be used.
To say mortal sin means mortal sin (all conditions are met). Mortal sin would not be so otherwise.
This is why I have brought up many times the bible verse, 1 Corinthians 6:19!
Paul speaks to the fact that murder, fornicators, theives, etc. will not inherit the Kingdom of Heaven. Now Paul **did not qualify the requirements, ergo, the subjective context, **when he said this. So Beth and others would be saying to Paul what is being said to me…that…“No, they are not mortal sins or “always” mortal sins if …”
But those who heard Paul understood that he meant deliberate commission of these acts.
We can also look at the Ten Commandments. There are no conditional reminders there either. One states, “You shall not commit murder.” You would then ask well “What if…”
Sure you can ask and should ask if you are unsure about your state but the Ten Commandments infer that you you are guilty if you commit murder. We don’t have to keep mentioning the three conditions when we speak in the objective context.
So to say, “Missing Mass is a mortal sin” is accurate because it is being used in the same context as Paul when he said that xyz sins are damning (mortal).
Just a refresher pasted from the Catechism:
*A mortal sin is any sin whose matter is grave and which has been committed willfully and with knowledge of its seriousness.
Grave matter includes, but is not limited to, murder, receiving or participating in an abortion, homosexual acts, having sexual intercourse outside of marriage or in an invalid marriage, and deliberately engaging in impure thoughts (Matt. 5:28–29). Scripture contains lists of mortal sins (for example, 1 Cor. 6:9–10 and Gal. 5:19–21). For further information on what constitutes a mortal sin, see the Catechism of the Catholic Church. *
You can see that the term mortal sin in the paragraph above is used both with an explanation of the requirements for it to be met AND it uses **mortal sins **to describe the sins in the verses shown,
with no requirements mentioned (their implied).
I hope this clears things up.