Conjugate Axes

...If the constant is 2a and the length of the line segment FF' is 2c , then e = c / a (>1) is called the eccentricity. The straight line FF' is called the horizontal axis, and the perpendicular bisector of the line segment FF' is called the conjugate axis, and together these are called the principal axis. The midpoint of the line segment FF' is called the center. ...

*Some of the terminology that refers to "conjugate axes" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…定数を2aとし，線分FF′の長さを2cとするとき，e＝c/a(＞1)を離心率という。直線FF′を横軸，線分FF′の垂直2等分線を共役軸といい，これらを合わせて主軸という。また，線分FF′の中点を中心という。…

※「共役軸」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報