Opus

Opus is a Latin word for work. The plural of opus is opera.

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.

In architecture, it specifically describes a technique or a method or a style of connecting building elements, following the studies on Roman architecture.

Roman building styles are commonly classified as:

Opus incertum
Opus testaceum (also called Opus latericium)
Opus caementicium
Opus reticulatum (also called Opus certum)
Opus siliceum
Opus quadratum
Opus vittatum
Opus mixtum
Opus spicatum
Opus alexandrinum

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.