Main Entry: ¹fo·cus

Pronunciation: \ˈfō-kəs\

Function: noun

Inflected Form(s): plural fo·ci \ˈfō-ˌsī also -ˌkī\ also fo·cus·es

Etymology: New Latin, from Latin, hearth

Date: 1644

1 a : a point at which rays (as of light, heat, or sound) converge or from which they diverge or appear to diverge; specifically : the point where the geometrical lines or their prolongations conforming to the rays diverging from or converging toward another point intersect and give rise to an image after reflection by a mirror or refraction by a lens or optical system b : a point of convergence of a beam of particles (as electrons)
2 a : focal length b : adjustment for distinct vision; also : the area that may be seen distinctly or resolved into a clear image c : a state or condition permitting clear perception or understanding <tried to bring the issues into focus> d : direction 6c <the team lost focus>
3 : one of the fixed points that with the corresponding directrix defines a conic section
4 : a localized area of disease or the chief site of a generalized disease or infection
5 a : a center of activity, attraction, or attention <the focus of the meeting was drug abuse> b : a point of concentration
6 : the place of origin of an earthquake or moonquake
7 : directed attention : emphasis

— fo·cus·less \-ləs\ adjective

— in focus : having or giving the proper sharpness of outline due to good focusing

— out of focus : not in focus