principal axis
noun
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.
Physics.
one of three mutually perpendicular axes of a body about which the moment of inertia is maximum or minimum.
Origin of principal axis
First recorded in 1875–80
Words nearby principal axis
British Dictionary definitions for principal axis
principal axis
noun
the line passing through the optical centre and centres of curvature of the faces of a lens or a curved mirror
any of three mutually perpendicular axes about which the moment of inertia of a body is maximum