semimajor axis

[ sem-ee-mey-jer, sem-ahy-, sem-ee-, sem-ahy- ]
/ ˈsɛm iˈmeɪ dʒər, ˈsɛm aɪ-, ˌsɛm i-, ˌsɛm aɪ- /

noun

Geometry. one half the major axis of an ellipse.
Astronomy. one half the major axis of the ellipse that one celestial body describes around another, as a planet around the sun or a satellite around a planet, equivalent to the mean distance between the two bodies.

Nearby words

  1. semilunar cartilage,
  2. semilunar conjunctival fold,
  3. semilunar ganglion,
  4. semilunar line,
  5. semilunar valve,
  6. semimatte,
  7. semimembranous,
  8. semimicroanalysis,
  9. semiminor axis,
  10. semimonthly

Origin of semimajor axis

First recorded in 1925–30; semi- + major

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019