noun
: a line through the center of a thin lens or through the center of curvature of a concave or convex mirror other than the principal axis of the lens or mirror
noun
: a line through the center of a thin lens or through the center of curvature of a concave or convex mirror other than the principal axis of the lens or mirror
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012