One of the mysteries of the English language finally explained.
1Geometry the line passing through the focus or foci of a conic section, perpendicular to the directrix.
2Optics the line which passes through the focal point (or points) of a curved mirror or lens and its centre; the line which passes through the centre of each lens in a compound lens, telescope, microscope, or other optical instrument.
Late 18th century.
In this article we explore how to impress employers with a spot-on CV.