semimajor axis

[ sem-ee-mey-jer, sem-ahy-, sem-ee-, sem-ahy- ]

noun

1. Geometry. one half the major axis of an ellipse.
2. 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.

Word History and Origins

Origin of semimajor axis¹

First recorded in 1925–30; semi- + major

Example Sentences

This bounce arises when a body reemits solar energy absorbed earlier in its day, causing a change to the object’s semimajor axis.

From Nature

This bounce arises when a body reemits solar energy absorbed earlier in its day, causing a change to the object’s semimajor axis.

From Scientific American