Tropic of Capricorn, parallel of latitude at 23°30' south of the equator; it is the southern boundary of the tropics. This parallel marks the farthest point south at which the sun can be seen directly overhead at noon; south of the parallel the sun appears less than 90° from the northern horizon at any day of the year. The sun reaches its vertical position over the Tropic of Capricorn at about Dec. 22, the summer solstice for the Southern Hemisphere. The term Capricorn comes from the Latin words caper [goat] and cornu [horn] and is the name given to one of the 12 constellations in the zodiac.
