Atrium
Etymology
Latin "atrium," the central hall or court of a Roman house, open to the sky. One old (and disputed) explanation ties it to "ater" (black), from the soot that once blackened the walls around its central hearth. Modern architecture revived the word for glazed, sky-lit interior courts.
noun · /AY-tree-uhm/
A large open central space within a building, often rising through several floors and lit from above.
What it names
The light-filled core of many modern offices, hotels, and museums — a room built out of emptiness — and links them to the open courtyard at the heart of the ancient Roman house.
Example
The hotel’s atrium runs the full height of the building, with glass elevators sliding up its walls.
Related idea
An atrium is a tall interior space usually enclosed and roofed, often in glass; a courtyard is an open-air space enclosed by walls but with the sky itself overhead. The atrium brings the light in; the courtyard leaves the roof off entirely.
noun · /AY-tree-uhm/
Either of the two upper chambers of the heart, which receive incoming blood and pass it down to the ventricles.
What it names
It reuses the architectural image of an open receiving hall for the body's own entry rooms, where blood arrives before being pumped onward.
Example
The right atrium collects oxygen-poor blood from the body and empties it into the right ventricle.
Related idea
Paired with the lower ventricle: the atrium is the receiving room where blood arrives, while the ventricle is the muscular pump that drives it onward.