Noun
One of the two points of an orbit, as of a planet or satellite, which are at the greatest and least distance from the central body, corresponding to the aphelion and perihelion of a planet, or to the apogee and perigee of the moon. The more distant is called the higher apsis; the other, the lower apsis; and the line joining them, the line of apsides.
In a curve referred to polar coordinates, any point for which the radius vector is a maximum or minimum.
Same as Apse.
Source: Webster's dictionaryThe difference in distance between Earth's nearest point to the Sun in January (for a table of these dates for various years, see Apsis ) and farthest point from the Sun in July is about 5 million kilometers (3.1 million miles). Source: Internet