DOO´-plecks
In flyover country, a duplex is a two-family home, usually divided down the center, and often rather downscale. But in larger cities, especially New York, a duplex is an apartment made of up two stories (or parts of two stories) of a high-rise building.
Because space is at such a premium in Manhattan, and in certain areas of other large cities, a duplex apartment—depending on its size, location, and amenities—is often considered an extreme luxury.
Bonus word: a triplex is an apartment composed of three stories.