The parallel of latitude approximately 66°33′ north. It forms the boundary between the North Temperate and North Frigid zones.
360 dergrees
Approximately 66° 33' 39" N marks the boundary of the Arctic Circle
66.5 degrees
You're talking about the 'Arctic Circle'.
The only state with part of its boundary defined by the arc of a perfect circle is Wyoming. The eastern boundary of Wyoming follows the 42nd parallel north latitude line, which forms part of a perfect circle around the Earth.
The parallel of latitude that circumscribes the polar tundra zone is the Arctic Circle in the northern hemisphere and the Antarctic Circle in the southern hemisphere. These circles mark the boundary where the tundra biome transitions into the polar ice caps.
The boundary or perimeter of a circle is its circumference.
That's close to an approximate latitude for the Antarctic Circle.
The imaginary line located at 66.5 degrees south latitude is called the Antarctic Circle. This is the southernmost latitude at which the sun can remain continuously above or below the horizon for 24 hours during the summer and winter solstices, respectively. It marks the boundary of the Antarctic region.
The Arctic Circle is a line of latitude. As of 2012, it is approximately 66° 33' 44" N latitude.
The "tropical latitudes" are the latitudes within 23.5 degrees of the equator, both north and south of it. The half of the "tropics" between the equator and the Arctic Circle is the half between the equator and 23.5 degrees north latitude. The line at 23.5 degrees north latitude that marks the northern boundary of the tropics is the "Tropic of Cancer".
The Arctic Circle is at 66 degrees 33 minutes N latitude.