Definition: Latin for “work.” Used with a number (e.g., Op. 28) to indicate the chronological order of a composer’s publication.
The Savvy Take: Opus numbers are great for understanding a composer’s life. Beethoven Op. 2 is young and fiery; Beethoven Op. 111 is deaf, transcendent, and complex. Knowing the Opus tells you which “version” of the composer you are dealing with.