semimajor axis

American  

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

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.

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Etymology

Origin of semimajor axis

First recorded in 1925–30; semi- + major

Example Sentences

What is the semimajor axis of a circle of diameter 24 cm?

From Textbooks • Oct. 13, 2016

It has a semimajor axis of 84 AU.

From Textbooks • Oct. 13, 2016

For example, the semimajor axis of the orbit of Mars, which is also the planet’s average distance from the Sun, is 228 million kilometers.

From Textbooks • Oct. 13, 2016

Jupiter’s orbital period is 11.86 years, and its semimajor axis is 5.20 AU.

From Textbooks • Oct. 13, 2016

Earth’s orbital period is 1.00 year, and its semimajor axis is 1.00 AU.

From Textbooks • Oct. 13, 2016