focus

—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.

[1635-45; < L: fireplace, hearth]

Syn. 1. center, heart, core, nucleus.

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