semimajor axis

noun

semi·​ma·​jor axis ˌse-mē-ˈmā-jər- 

ˌse-ˌmī-,

-mi-

: one half of the major axis of an ellipse (such as that formed by the orbit of a planet)

Examples of semimajor axis in a Sentence

Recent Examples on the Web

The uncertainty in its semimajor axis (the radius of its orbit at its two most separated points) is just six meters out of a total length of 168,505,699.049 kilometers. —Dante S. Lauretta, Scientific American, 1 Aug. 2016

Word History

First Known Use

1818, in the meaning defined above