The Tropic of Cancer is one of the five major circles of latitude that mark maps of the Earth. This is the parallel of latitude that runs approximately 23.5° north of the Equator, and is the farthest northern latitude at which the sun can appear directly overhead. North of this line is the Northern Temperate Zone. South of this line are the Tropics. This line is called the Tropic of Cancer because, when the sun appears directly overhead, at this latitude, during the summer solstice, it is entering the zodiac sign of Cancer.
Tropic of Cancer is also the name of a book written by Henry Miller and first published in 1934.