The three major sub-divisions of “Catholic”, “Orthodox”, and “Protestant” are, in my opinion, much to vague. There are many denominations that don’t rightfully fit into any of the three. For example, the Assyrian Church is a very ancient Christian body that is not in full communion with any other church, and has not been since the early 5th century (long before the Eastern Orthodox). The Oriental Orthodox Churches (Armenian, Syriac, Coptic, Ethiopian, Eritrean, and Indian Orthodox Churches) are also a separate group, not in full communion with the Eastern Orthodox Churches, and should be counted as a separate group for they have been in schism for roughly 1500 years, as opposed to the mere 1000 years that the Eastern Orthodox Church has been in schism. Then we have the dozens (or hundreds?) of ‘independent catholic’ and schismatic catholic churches. There are dozens “Independent Catholic” denominations that are not Protestant, Orthodox, nor Catholic (n the true sense). They have the 7 sacraments, they have a priesthood and the episcopate…but they are of recent origin (relatively), and are Western, not Eastern, and they all reject the papacy. Some of them accept the first 4 ecumenical councils, others the first 7. (And there are probably some in between). These include such obscure churches as the “United Catholic Church”, “Apostolic Catholic Church”, “American Catholic Church”, so-called “primitive Catholics”, and dozens of other groups. They have different histories and origins, but many have connections to the Old Catholic Church. Some, maybe even many of them, may have apostolic succession, as they often can trace their lines back to Roman Catholic or Eastern Orthodox bishops. (
campusprogram.com/reference/en/wikipedia/o/ol/old_catholic_church.html, claims that many “independent catholic” churches only exist on the net, not in real life…because there may be hundreds of ones represented online).
Then we have schismatic Catholics who recognize all the councils except for perhaps the last two, or the most recent one.
Two other important ‘independent catholic’ churches that come to mind are the Philippine Independent Church (which broke off directly from the Roman Catholic Church around 1900 I believe), and the Polish National Catholic Church (which was actually originally founded in America in the late 19th century, if I recall correctly).
The Old Catholic Church, which I mentioned above, should also be noted. Apparently it is in full communion with the Anglican Communion. Here’s some info on it
campusprogram.com/reference/en/wikipedia/o/ol/old_catholic_church.html, and
alt-katholisch.de/index-e.html is the official site (I think?).
Here’s a good, but far from comprehensive breakdown of denominations within Christendom.
campusprogram.com/reference/en/wikipedia/l/li/list_of_christian_denominations.html
God bless