The tropics are the geographic region of the Earth limited in latitude by the two tropics: the Tropic of Cancer and the Tropic of Capricorn, and thus centered on the equator. This area lies approximately between 23.5° N latitude and 23.5° S latitude, and includes all the parts of the Earth where the sun reaches a point directly overhead at least once during the solar year (north of the Tropic of Cancer and south of the Tropic of Capricorn the sun never reaches an azimuth of 90° or directly overhead). The word "tropics" comes from Greek tropos meaning "turn".
Tropical plants and animals are those species native to the tropics. Tropical is also sometimes used in a general sense of a place that is warm and moist year-round, often with the sense of lush vegetation. However, there are places in the tropics that are anything but "tropical" in this sense, even with alpine tundra and snow-capped peaks! (See, for example, Mauna Kea).
In Köppen's scheme of climate classification, a tropical climate is defined as a non-arid climate in which all twelve months have mean temperatures above 18 °C (64.4 °F).
See also : tropical year; tropical medicine