In Apostles’ Creed we say ““I believe in … the holy catholic Church…” In Nicene Creed we say “I believe in one, holy, catholic and apostolic Church.”
Roman Catholic Church has various rites — Latin, Ambrosian, Mozarabic, Alexadrian, Byzantine, Chaldean, Maronite, Melkite, Ruthenian, Syro-Malabar, Syro-Malankara, Ukrainian and so on. Since some years rites are referred by some people as churches. This is contrary to the creeds and creates confusion. There are Orthodox and Protestant Churches. There is Anglican Communion. There are free churches. When one says Ukrainian Church one is not sure whether it is Catholic or Orthodox. When one says Syrians Christians it is not clear whether he refers to Catholics or Jacobites.
Roman Catholic Church claims it is the true church and others separated from it. Others claim they are divided Christians, not separated Christians. For Roman Catholic Church it is not proper to speak of churches within itself except for church buildings. Referring to dioceses as particular churches should be avoided.