Final answer:
Opera was originally meant to describe a 'song drama' or 'music drama' that encompasses music, singing, and acting set to an orchestral score, different from ballet, symphony, and concerto, which focus on dance and instrumental compositions.
Step-by-step explanation:
The term ‘opera’ was originally meant to describe what can be referred to as a ‘song drama’ or ‘music drama.’ This art form combines storytelling through music, singing, and acting, set to an orchestral score. Historically, opera has been a vital part of theatrical traditions, often including an integration of various elements such as dance, scenic design, costumes, and sometimes even verse. The tradition of opera dates back to the 16th century in Italy and has since spread and evolved across the world. It can be seen in European classics, Asian forms such as the Chinese Peking Opera, and further contributed to the evolution of modern musical theatre.
Other forms of musical theater, which also evolved from the storytelling traditions, include ballet, symphony, and concerto. However, they have different focuses; ballet is primarily a dance form with music but may or may not include lyrics or acting; symphony is a longer instrumental composition typically for orchestra; and concerto is a composition showcasing a soloist or group of soloists contrasted with an orchestra. These, while related to opera in the sense that music plays a central role, are distinct in their own artistic means and ends.