Duomo is an Italian term for a church with the features of, or having been built to serve as, a cathedral, whether or not it currently plays this role. Monza Cathedral, for example, has never been a diocesan seat and is by definition not a cathedral. On the other hand, the city of Trevi no longer has a bishop, although it once did, and the erstwhile cathedral of Emilianus of Trevi is now a mere church. By contradistinction, the Italian word for a cathedral sensu stricto is cattedrale.
