/ ˈəʊpəs; NAmE ˈoʊ-/ noun ( pl. opera / ˈɒpərə; NAmE ˈɑːp-/) [ usually sing. ]
1.
( abbr. op. ) a piece of music written by a famous composer and usually followed by a number that shows when it was written :
Beethoven's Opus 18
2.
( formal ) an important piece of literature, etc., especially one that is on a large scale
SYN work
—see also magnum opus
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WORD ORIGIN
early 18th cent.: from Latin , literally work .