It is used in many fields, notably in architecture and in music. In music, pieces of some composers' music are given opus numbers which generally run either in order of composition or in order of publication.
Roman building styles are commonly classified as:
Opus Dei (God's work) is a conservative Roman Catholic organization founded in 1928.
Opus the penguin is a character in the cartoon strip Bloom County.
A "magnum opus" (or "opus magnum") is a great work or, more commonly, the greatest work of a person. Magnum is Latin for great.