principal axis

noun

1. Optics.,  a line passing through the center of the surface of a lens or spherical mirror and through the centers of curvature of all segments of the lens or mirror.

2. Physics.,  one of three mutually perpendicular axes of a body about which the moment of inertia is maximum or minimum.

principal axis

noun

1. the line passing through the optical centre and centres of curvature of the faces of a lens or a curved mirror

2. any of three mutually perpendicular axes about which the moment of inertia of a body is maximum

Word History and Origins

Origin of principal axis¹

First recorded in 1875–80