Aphelion

Aphelion, that point in the elliptical orbit of a planet which is most remote from the sun. The opposite point, or that nearest to the sun, is styled the Perihelion. At the former point, the swiftness of the planet's motion is least, and begins to increase; at the latter, it is greatest, and begins to decrease. This irregularity of motion is most remarkable in comets whose orbits deviate most from the circle. The word is a Grecised form of Kepler's Lat. aphelium, from Gr. apo, 'from,' and hēlios, 'sun.' See APSIDES, ORBIT.