opus
n.a major work of art, music, or literature. It is often used to describe a very important or large project that a creator has finished.
n.a creative work, especially a musical composition or a literary production, numbered to indicate the order of a composer's works. Often refers to a large-scale or significant achievement within an artist's career.
“This symphony is considered the composer's greatest opus.”
“After ten years of research, the professor finally published his historical opus on the industrial revolution.”
“While his early sketches showed promise, it was this sprawling, three-volume opus that secured his reputation as the preeminent novelist of his generation.”
The plural form can be 'opuses' or the Latin 'opera'.
Borrowed from Latin opus.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.