Tropics
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The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the northern hemisphere and the Tropic of Capricorn in the southern hemisphere. The tropics are also called the tropical zone and the torrid zone.
This area lies approximately between 23°30'/23.5° N latitude and 23°30'/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. (In the temperate zones, north of the Tropic of Cancer and south of the Tropic of Capricorn, the sun never reaches an altitude of 90° or directly overhead.) The word "tropics" comes from Greek tropos meaning "turn", because the apparent position of the Sun oscillates between the two tropics with a period that defines the average length of a year.
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, with even alpine tundra and snow-capped peaks, including Mauna Kea, Mt. Kilimanjaro, and the Andes as far south as the northernmost parts of Chile and Argentina.
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 how directness of sunlight causes warmer weather.