Opera
* Typically tells a serious or tragic story
* Uses classical music and operatic singing
* Has a large cast of characters and a full orchestra
* Is typically performed in a large opera house
Operetta
* Typically tells a light-hearted or comedic story
* Uses popular or folk music and operetta-style singing
* Has a smaller cast of characters and a smaller orchestra
* Is typically performed in a smaller theater
Of course, there can be some overlap between opera and operetta. Some operas can have comedic elements, and some operettas can have serious or dramatic moments. However, in general, opera and operetta are two distinct genres of musical theatre.