An oratorio is a long piece of music in which a large group of people sing — usually a choir, with solo singers and an orchestra too. The story is often religious. People sit and listen; the singers do not usually wear costumes or act the story on a stage the way they do in an opera. Handel’s Messiah is the example most English speakers know. You will meet the word in concert notes, music class, and church programmes more than in the street. Though actually, the name comes from the Italian for a kind of prayer hall: that is where this music was first sung, which is why oratorio and oratory are twins from the same Latin word.