'Opera' is the plural of Latin 'opus' (work) — short for 'opera in musica,' a work performed in music.
A dramatic work set to music for singers and instrumentalists, combining text (libretto), music, staging, and often dance.
From Italian 'opera,' short for 'opera in musica' (a work in music), from Latin 'opera' (work, effort, service), the plural of 'opus' (work). The Latin 'opus' derives from Proto-Indo-European *h₃ep- (to work). The term arose in early seventeenth-century Italy when composers in Florence developed a new art form — staged drama set entirely to music. They needed a name for this new creation, and 'opera' (literally just 'work' or 'works') was adopted
The word 'opera' is literally the plural of 'opus' — so etymologically, an opera is not 'a work' but 'works,' reflecting the composite nature of the art form that combines multiple works (music, poetry, staging, dance) into a single production. It may be the most generic name for any art form: it literally just means 'stuff.'