Perhaps someone can define the two terms for me then showing their distinction ? …
Hello,
I gave a basic distinction but will try to flesh it out a little. First, know that these are matters addressed by canon law. A denial of Communion can be carried out according to canon #915 of the Code of Canon Law. Excommunication is defined in canon #1331.
As I said, excommunication is a penalty resulting from a criminal action. It can only apply to Catholics. Excommunication can result from such crimes as directly violating the seal of Confession, committing heresy, physically attacking the Pope, actually procuring an abortion, etc. There are many conditions which must be met before such a penalty could be incurred and/or imposed. (This is getting too technical and doesn’t really matter here). The result of an excommunication is that the (lay) person is prohibited from receiving any Sacraments and having any ministerial participation in any public worship. Necessarily, such a person is not to receive Communion while in a state of excommunication. The problem is that the offense might not be public. For example, lets say a Catholic, fully aware of what he is doing and of the consequences of his action, makes it known to his spouse that he is a heretic. He tells no one else and neither does she. The next day, he goes to Communion. The priest has no reason to deny him the Sacrament and, based on what he knows, he cannot deny it. Yet, that man is excommunicated automatically due to heresy. He is committing a further sin by receiving Communion in that state but the priest has no way of knowing that.
On the other hand, a person can be denied Holy Communion due to publicly known, persistent, grave sin. Let’s say a man is a well-known mafia boss (the sort of person the Pope recently warned to reform his ways or he will end up in hell). He’s in prison for murder, etc., and has shown no sign of repentance. If the priest goes to the prison to say Mass and that man attempts to receive Communion, the priest should deny him. This is not because of excommunication (there is no excommunication for murder) but because of his manifest, obstinate persistence in grave sin. Strictly speaking, he is not being subjected to a penalty. It could happen, also, that a non-Catholic could be denied Communion. Someone who is not baptized, for instance, cannot receive any Sacraments except baptism. Since non-Catholics can never be given a penalty such as excommunication, this denial is not a penalty. It is discipline, based on theology.
Sometimes, a person who has been excommunicated will also be obstinately persisting in manifest grave sin–maybe the heretic goes public on a series of talk shows, broadcasting his heresy. Maybe that mob boss is actually an apostate. So, there could be some overlap in individual cases.
This link, in number 6, makes the distinction between a denial of Communion and a penalty:
ewtn.com/library/CURIA/cdfworthycom.htm
In general, this is the most authoritative statement on how canon 915 (denial of Communion even if not excommunicated) should be applied, especially in #2-4:
vatican.va/roman_curia/pontifical_councils/intrptxt/documents/rc_pc_intrptxt_doc_20000706_declaration_en.html
Dan