Earth & SkyGreek → English
Apsis
/ˈæpsɪs/noun
Either of the two points in an orbit where a body is nearest to or farthest from the object it circles.
The Greek roots
ἁψίς
hapsís
loop, arch, wheel rim
Literally: “a fastening, a loop”
Follow a root:ἁψίς7 words
The story of the word
ἁψίς meant a loop, then the rim of a wheel, then an arch, all from ἅπτειν, to fasten. Astronomers kept it for the two turning points of an elliptical orbit, and the straight line joining them is the line of apsides, which slowly rotates. The apse at the east end of a church is the same word taken through Latin, and haptic comes from the same verb in its other sense, to touch.
- How it travelled
- Ancient Greek → Latin → English
- First recorded
- 17th century
Same family
apseapoapsisperiapsishaptic
In a sentence
Mercury's line of apsides shifts a little more each century than Newton allows for.