noun
opus
OH-puhs/ˈəʊpəs/
An artistic work, especially a musical composition.
The bound score of the composer's opus lies beside a violin.

Etymology
Latin opus could mean labor or a work produced. English uses the word especially for a musical or literary composition, treating the finished creation as a “work.”
In context
his magnum opus that is his um his best work the Fresco cycle
More examples
- The orchestra performs her latest opus tonight.
- His first novel is a sprawling opus about family life.
- This sonata is listed as opus 12 in the catalog.
Forms
opus · opuses · opera
composition noun — An original piece of written music.