Definition and etymology
The word Arctic comes from the Greek word ἀρκτικός (arktikos), "near the Bear, northern" and that from the word ἄρκτος (arktos), meaning bear. The name refers either to the constellation Ursa Major, the "Great Bear", which is prominent in the northern portion of the celestial sphere, or to the constellation Ursa Minor, the "Little Bear", which contains Polaris, the Pole star, also known as the North Star.
There are a number of definitions of what area is contained within the Arctic. The area can be defined as north of the Arctic Circle (66° 33'N), the approximate southern limit of the midnight sun and the polar night. Another definition of the Arctic is the region where the average temperature for the warmest month (July) is below 10 °C (50 °F); the northernmost tree line roughly follows the isotherm at the boundary of this region.