N-COUNT
(按创作的先后次序排列的某一作曲家的)编号作品(缩略形式为op.)
An opus is a piece of classical music by a particular composer. Opus is usually followed by a number which indicates at what point the piece was written. The abbreviation op. is also used.
例句
...Beethoven's Piano Sonata in E minor, Opus 90.
贝多芬的第90号E小调钢琴奏鸣曲