1911 Encyclopædia Britannica/Solstice
SOLSTICE (Lat. solstitium, from sol, sun, and sistere, to stand still), in astronomy either of the two points at which the sun reaches its greatest declination north or south. Each solstice is upon the ecliptic midway between the equinoxes, and therefore 90° from each. The term is also applied to the moment at which the sun reaches the point thus defined.