foci


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fo·ci

 (fō′sī′, -kī′)
n.
A plural of focus.

fo•cus

(ˈfoʊ kəs)

n., pl. -cus•es, -ci (-sī, -kī), n.
1. a central point, as of attention or activity.
2. a point at which rays of light, heat, or other radiation meet after being refracted or reflected.
3.
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: out of focus.
4. (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.
5. the point of origin of an earthquake.
6. 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; < Latin: fireplace, hearth]
fo′cus•a•ble, adj.
References in classic literature ?
At first, no result at all crowned my efforts, though I 'divided my swift mind,' now hither, now thither, in a way that I felt sure would have made AEneas green with envy: but the dimly-seen oval remained as provokingly blank as ever--a mere Ellipse, as if in some mathematical diagram, without even the Foci that might be made to do duty as a nose and a mouth.