Generally, yes. If you are referring to the Catholic Church, then “Catholic” and “Church” should be capitalized since they refer to a proper noun. If you are referring to someone who practices Catholicism, then you should capitalize Catholic as well.
When would you lowercase Catholic?
When it first entered the English language in the 16th century, catholic meant “common” or “general” so the religion was naturally the “common” religion. When the Western Church split from the rest of the church after the Reformation, it began referring to itself as the Catholic Church, but the word catholic still meant “general” or “common” when used by itself.
What about Catholicism?
Since Catholicism is a noun referring to the Catholic religion, it is capitalized as well.
To learn more about proper title capitalization rules, give our free title capitalization tool a try.
This is a fine explanation of when to capitalize the word “catholic,” except the historical explanation is incorrect. The “Western Church” did not split from the rest of the Church during the Protestant Reformation. The “Western Church” referred to here is the “One, Holy, Catholic, and Apostolic Church” in the Nicene Creed. Additionally, it is wrong to say that the Church only began referring to itself as the Catholic Church after the Protestant Reformation. In his letter to the Smyrnaeans in 110 AD, St. Ignatius of Antioch first called the Church Catholic:
“Flee from schism as the source of mischief. You should all follow the bishop as Jesus Christ did the Father. Follow, too, the presbytery as you would the apostles; and respect the deacons as you would God’s law. Nobody must do anything that has to do with the Church without the bishop’s approval. You should regard that Eucharist as valid which is celebrated either by the bishop or by someone he authorizes. Where the bishop is present, there let the congregation gather, just as where Jesus Christ is, there is the Catholic Church. Without the bishop’s supervision, no baptisms or love feasts are permitted. On the other hand, whatever he approves pleases God as well. In that way everything you do will be on the safe side and valid.”
Here is his letter the word “catholic” in Greek is an adjective no the noun “Catholic” my question is when catholic became Catholic that’s what I want to know! (Check the Greek and if it is necessary to check different editions published because the son of them add C another use c and the last word is the original manuscripts.