Besides being the name of a cartoon penguin, “opus” is a word used to refer to a creative work, usually musical and of considerable scope (as in a “magnum opus”). The term comes from the Latin word for work. Musical compositions are given an “opus number,” such as Beethoven’s Opus 125, also known as his Ninth Symphony. In this usage, the word is usually abbreviated as “op,” a common sight on classical music recordings.
Of particular interest is the plural of this word: opera, meaning works. This is why compositions that include music, dance, scenery and costumes are called operas, as they combine works form various disciplines in the arts. Other common words from this root are operate (as in surgery, or medical work), and the operating system of your computer, which makes it work.
While we’re talking about music and operas, why do we yell “bravo!” at the end of a particularly fine performance? This word comes from the Italian for “good.” If you really like a performance, you can yell “bravissimo!,” which expresses approval in the extreme (“most excellent!”). Or you could just yell “excellent!” or “awesome!,” but you’d likely get some unwelcome stares for your faux pas (French: false step).