Either of the two moments in the year when the Sun's apparent path is farthest north or south from Earth's Equator; also, either of the two points along the ecliptic that the Sun passes through at these times.
In the Northern Hemisphere the summer solstice occurs on June 21 or 22; the winter solstice on December 21 or 22. In the Southern Hemisphere the seasons are reversed. See also equinox .