apsis

apsis Definition

ap·sis (ap′sis)

noun pl. -·si·des′-sə dēz′

that point in the elliptical orbit of the moon, a planet, etc. nearest to (lower apsis), or that farthest from (higher apsis), the gravitational focus point
apse (sense )

Etymology: L, an arch < Gr hapsis, a fastening < haptein: see apt

apsis Idioms

line of apsides

a line joining the lower and higher apsides, forming the major axis of the orbit

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