The 18th century lexicographer and critic Dr Johnson described opera as an “exotic and irrational entertainment”. By “exotic” he meant that it came from a foreign country (which in those days was true: all opera at the time came from Italy). By “irrational” he meant that the things which happened in the stories were strange and not like real life. A play can be like real life, but an opera is being sung, so things are not going to happen like they normally do in real life. A singer might be singing “I must go, I must go!” and he may stand on the stage and sing this for several minutes before at last he goes! A singer may be pretending to die, and will sing a beautiful song before he or she finally dies. These things are “conventions”, which means that they are a kind of habit we have to accept when watching and listening to opera. Another convention of earlier operas was to have the part of young men sung by women. This is sometimes called a breeches role or trouser role. They are often small parts such as page boys, or teenagers who flirt with older women, such as the part of Cherubino in Mozart’s " The Marriage of Figaro" or Oktavian in Richard Strauss’s "Der Rosenkavalier". It should be remembered that in the 18th century it was usual for the main female part to be sung by a man who was a castrato.