—focusable, adj. —focuser, n./foh"keuhs/, n., pl. focuses, foci /-suy, -kuy/, v., focused, focusing or (esp. Brit.) focussed, focussing.n.1. a central point, as of attraction, attention, or activity: The need to prevent a nuclear war became the focus of all diplomatic efforts.2. Physics. a point at which rays of light, heat, or other radiation, meet after being refracted or reflected.3. Optics.a. the focal point of a lens.b. the focal length of a lens.c. the clear and sharply defined condition of an image.d. the position of a viewed object or the adjustment of an optical device necessary to produce a clear image: in focus; out of focus.4. Geom. (of a conic section) a point having the property that the distances from any point on a curve to it and to a fixed line have a constant ratio for all points on the curve. See diag. under ellipse, hyperbola, parabola.5. Geol. the point of origin of an earthquake.6. Pathol. the primary center from which a disease develops or in which it localizes.v.t.7. to bring to a focus or into focus: to focus the lens of a camera.8. to concentrate: to focus one's thoughts.v.i.9. to become focused.Syn. 1. center, heart, core, nucleus.
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