Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun principal_axis

1 sense of principal axis

Sense 1
principal axis, optic axis -- (a line that passes through the center of curvature of a lens so that light is neither reflected nor refracted; "in a normal eye the optic axis is the direction in which objects are seen most distinctly")
       => axis -- (a straight line through a body or figure that satisfies certain conditions)