Penthouse
A Penthouse is typically an apartment on the highest floor of an apartment building. It usually takes up less than half of the entire (flat) roof of the building. Originally the word penthouse meant a small building with a sloped roof. The modern use of the word started in the 1920s in America. In the age of skyscrapers the "house" on the roof was called a penthouse. A penthouse can also be commercial space.