Definition

Noun: The longest diameter of an ellipse or an ellipsoid. It is the line segment that passes through the center and both foci, representing the greatest width of the figure.

Usage

The term "major axis" is used in geometry, astronomy, and engineering to describe the primary dimension of an elliptical shape. - In geometry, it defines the key parameter for calculating an ellipse's area and eccentricity. - In astronomy, it often describes the orbit of a planet or satellite.

Examples

• Geometry:

  • The length of the major axis of the ellipse is 10 centimeters.
  • To draw an ellipse accurately, you must first determine its major axis.

• Astronomy:

  • The planet's major axis is so large that its orbit takes 165 Earth years to complete.
  • A comet's orbit can have a very elongated major axis.

Advanced Usage

• "Semi-major axis": This is half the length of the major axis, extending from the center to the ellipse's perimeter. It is a fundamental parameter in orbital mechanics.
  • The semi-major axis of Earth's orbit is one astronomical unit (AU).

Variants and Related Words

• Minor Axis (noun): The shortest diameter of an ellipse, perpendicular to the major axis at the center.
• Ellipse (noun): A closed curve where the sum of the distances from any point on the curve to two fixed points (foci) is constant.
• Focus (noun, plural: foci): One of the two fixed points used to define an ellipse, through which the major axis passes.

Synonyms

• Longest diameter (of an ellipse/ellipsoid)
• Principal axis (in the context of ellipses)

Related Phrases

• Axis of symmetry: A line about which a geometric figure is symmetric. The major axis is one axis of symmetry for an ellipse.

Noun

1. the longest axis of an ellipse or ellipsoid; passes through the two foci