| Term: | Antarctic circle |
| Definition: | The line of latitude 66 deg 34 min S (often taken as 66S). Along this line the sun does not set on the day of the summer solstice, about 22 December, and does not rise on the day of the winter solstice, about 21 June. |
| Term: | Antarctic circle |
| Definition: | Latitude of 66.5 South. The northern limit of the area of the Earth that experiences 24 hours of darkness or 24 hours of day at least one day during the year. |