The Nicene-Constantinopolitan Creed, professed by Ro-man Catholics each Sunday and solemnity, recognizes that the church is one, holy, Catholic, and apostolic. These significant terms, often referred to as the four marks of the church, not only describe fundamental qualities of Catholicism but also are foundational to how it has been understood over the Christian era and is organized today. It is important, therefore, to understand what these terms mean and signify in Roman Catholicism today.