A
tower block,
high-rise,
apartment tower,
residential tower,
apartment block,
block of flats, or
office tower is a tall
building or structure used as a
residential and/or
office building. In some areas it may be referred to as an "MDU", standing for "Multi Dwelling Unit". In the United States, such a structure is referred to as an
apartment building or
office building, while a group of such buildings is called an
apartment complex or
office complex.