A skyscraper is a tall continuously habitable building having multiple floors. Modern sources currently define skyscrapers as being at least 100 metres or 150 metres in height, though there is no universally accepted definition. Skyscrapers are very tall high-rise buildings. Historically, the term first referred to buildings with between 10 and 20 stories when these types of buildings began to be constructed in the 1880s. Skyscrapers may host offices, hotels, residential spaces, and retail spaces.
One common feature of skyscrapers is having a steel framework that supports curtain walls. These curtain walls either bear on the framework below or are suspended from the framework above, rather than resting on load-bearing walls of conventional construction. Some early skyscrapers have a steel frame that enables the construction of load-bearing walls taller than of those made of reinforced concrete.
Modern skyscrapers' walls are not load-bearing, and most skyscrapers are characterised by large surface areas of windows made possible by steel frames and curtain walls. However, skyscrapers can have curtain walls that mimic conventional walls with a small surface area of windows. Modern skyscrapers often have a tubular structure, and are designed to act like a hollow cylinder to resist wind, seismic, and other lateral loads. To appear more slender, allow less wind exposure and transmit more daylight to the ground, many skyscrapers have a design with setbacks, which in some cases is also structurally required.
As of January 2020[update], only nine cities in the world have more than 100 skyscrapers that are 150 m (492 ft) or taller: Hong Kong (355), Shenzhen (289), New York (284), Dubai (201), Shanghai (163), Tokyo (158), Mumbai (151), Chicago (130), Chongqing (127), and Guangzhou (118).