Catholic
1) Catholic means universal or whole. It is in this sense that all Christians may use it, including Protestants, often in lower case. The word dates from the patristic fathers to appeal to the whole body of believers, as opposed to mere sects or heretical creeds.2) In countries which have been traditionally Protestant, Catholic Church will be included in the official name of a particular parish church belonging to the Church of Rome in order to distinguish it from other denominations. For example, the name "St. Mark's Catholic Church," makes it clear that it is not an Episcopal or Lutheran Church. Using the word to name an organization arose when Protestantism appeared and it expressed the feeling that only one following the Roman rule can be part of the universal or catholic Body of Christ. From long use, Catholic has become shorthand for the Roman Church used by Protestant and Catholic alike. Orthodox churches still favor using the more accurate "Western Church" or "Latin Church" in reference to the Roman Catholic Church.
3) The formal language One Holy Catholic and Apostolic Church is favored by liturgical denominations, such as the Eastern Orthodox Churches and the Anglican Churches -- and of course, by Roman Catholics. The term "Apostolic" refers to the laying on of hands when consecrating a priest. It is a gesture of an unbroken oral heritage from the original twelve apostles up to the present. Also among these may be placed the Ancient Catholic Church, Old Catholic Church, Liberal Catholic Church and the Chinese Patriotic Catholic Association.
4) Catholic Church may refer to any of a number of other groups which do not recognize the supremacy of the Bishop of Rome but wish to distinguish themselves from Calvinistic or Puritanical tendencies in the Church. Typical among these are "High Church" Anglicans, i.e., "Anglo-Catholics"). Often, this will be printed Catholic Church, but sometimes, only "Church" will be capitalized.
5) The phrase "catholic epistles" is sometimes used to refer to the General Epistles of the Christian New Testament in the Bible, because these epistles were not addressed to any particular city but to all in general. This use reflects its Greek derivation and has nothing to do with a modern organization.
Capitalization is no sure guide to denominational affiliation. It may indicate formal affiliation with the Roman Church or it may not. More commonly, capitalization indicates the holy and solemn nature of the spiritual body of believers. It emphasizes the desire for all Christians to be one. In that sense, it is ironic that a term designating the whole church should apply to one human organization only.
The only sure rule is that if "catholic" is not capitalized, it is not Roman Catholic.
Many Protestant Christian churches -- especially Evangelicals -- avoid the term completely for what they believe is an important point of faith: no mortal man can be head of the universal Body of Christ. Wrongly or rightly, they believe that to suggest that the Pope could occupy such a position is heretical and a historical innovation dating only since the Great Schism. The Orthodox churches, of course, agree. Thus for some, to use the word "catholic" at all is to appear to give credence to Papal arrogance.