Medical Dictionary


noun fo·cus \ˈfō-kəs\
plural fo·ci \ˈfō-ˌalso -ˌkī\ also fo·cus·es

Medical Definition of FOCUS

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)
a :  focal length b :  adjustment for distinct vision; also :  the area that may be seen distinctly or resolved into a clear image
:  a localized area of disease or the chief site of a generalized disease or infection
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