How do you define different show types?
Musical: A production in which music, singing, and dancing are often integral components to storytelling.
Play: A production which generally sticks to spoken dialogue in order to tell a story.
Operetta: A short opera containing spoken dialogue, usually on a light or comedic subject. Differs from a musical in that vocal style is still closely aligned with that of opera, and in that operetta rarely includes complicated dancing.
Opera: A dramatic work for the stage for singers and instrumentalists, set completely to music. Occasionally, opera may include some spoken dialogue (examples: Die Zauberflöte and the original production of Carmen), but usually this is replaced by recitative (singing in the style of speaking).