focus

noun

a central point, as of attraction, attention, or activity: The need to prevent a nuclear war became the focus of all diplomatic efforts.

Physics. a point at which rays of light, heat, or other radiation, meet after being refracted or reflected.

Optics.

the focal point of a lens.

the focal length of a lens.

the clear and sharply defined condition of an image.

the position of a viewed object or the adjustment of an optical device necessary to produce a clear image: in focus; out of focus.

Geometry. (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.

Geology. the point of origin of an earthquake.

Pathology. the primary center from which a disease develops or in which it localizes.

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verb (used with object)

to bring to a focus or into focus: to focus the lens of a camera.

to concentrate: to focus one's thoughts.

00:10

Focus is always a great word to know.

So is quadratic formula. Does it mean:

formula for the roots of a quadratic equation

system in which the location of a point is given by coordinates

LEARN MORE UNUSUAL WORDS WITH WORD DYNAMO...

verb (used without object)

to become focused.

Origin:
1635–45; < Latin: fireplace, hearth

Related forms

fo·cus·a·ble, adjective

fo·cus·er, noun

mis·fo·cus, verb, mis·fo·cused, mis·fo·cus·ing or ( especially British ) mis·fo·cussed, mis·fo·cus·sing.

mis·fo·cused, adjective

mis·fo·cussed, adjective

o·ver·fo·cus, verb (used with object), o·ver·fo·cused, o·ver·fo·cus·ing or ( especially British ) o·ver·fo·cussed, o·ver·fo·cus·sing.

re·fo·cus, verb, re·fo·cused, re·fo·cus·ing or ( especially British ) re·fo·cussed, re·fo·cus·sing.

self-fo·cused, adjective

self-fo·cus·ing, adjective

self-fo·cussed, adjective

self-fo·cus·sing, adjective

un·fo·cus·ing, adjective

un·fo·cus·sing, adjective

well-fo·cused, adjective

well-fo·cussed, adjective

Synonyms
1. center, heart, core, nucleus.

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2013.
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Link To focus

Collins

World English Dictionary

focus (ˈfəʊkəs)

—n , pl -cuses, -ci
1.	a point of convergence of light or other electromagnetic radiation, particles, sound waves, etc, or a point from which they appear to diverge
2.	focal point another name for focal length
3.	optics the state of an optical image when it is distinct and clearly defined or the state of an instrument producing this image: the picture is in focus; the telescope is out of focus
4.	a point upon which attention, activity, etc, is directed or concentrated
5.	geometry a fixed reference point on the concave side of a conic section, used when defining its eccentricity
6.	Compare epicentre the point beneath the earth's surface at which an earthquake or underground nuclear explosion originates
7.	pathol the main site of an infection or a localized region of diseased tissue

—vb (often foll by on) , -cuses, -ci, -cuses, -cusing, -cused, -cusses, -cussing, -cussed
8.	to bring or come to a focus or into focus
9.	to fix attention (on); concentrate

[C17: via New Latin from Latin: hearth, fireplace]

'focusable

—*adj*

'focuser

—n

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Etymonline

Word Origin & History

focus

1640s, from L. focus "hearth, fireplace," of unknown origin, used in post-classical times for "fire" itself, taken by Kepler (1604) in a mathematical sense for "point of convergence," perhaps on analogy of the burning point of a lens (the purely optical sense of the word may have existed before Kepler,

but it is not recorded). Introduced into English 1650s by Hobbes. Sense transfer to "center of activity or energy" is first recorded 1796. The verb is first attested 1814 in the literal sense; the figurative sense is recorded earlier (1807). Related: Focused; focusing; focussed; focussing.

Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage

Medical Dictionary

focus fo·cus (fō'kəs)
n. pl. fo·cus·es or fo·ci (-sī', -kī')

A point at which rays of light or other radiation converge or from which they appear to diverge, as after refraction or reflection in an optical system. Also called focal point.
See focal length.
The distinctness or clarity of an image rendered by an optical system.
The state of maximum distinctness or clarity of such an image.
An apparatus used to adjust the focal length of an optical system in order to make an image distinct or clear.
The region of a localized bodily infection or disease.

v. fo·cused or fo·cussed, fo·cus·ing or fo·cus·sing, fo·cus·es or fo·cus·ses

To cause light rays or other radiation to converge on or toward a central point; concentrate.
To render an object or image in clear outline or sharp detail by adjustment of one's vision or an optical device.
To adjust a lens or instrument to produce a clear image.
To converge on or toward a central point of focus; be focused.

American Heritage

Science Dictionary

focus

(fō'kəs) Pronunciation Key
Plural focuses or foci (fō'sī', fō'kī')

The degree of clarity with which an eye or optical instrument produces an image.
See focal point.
A central point or region, such as the point at which an earthquake starts.
Mathematics A fixed point or one of a pair of fixed points used in generating a curve such as an ellipse, parabola, or hyperbola.
The region of a localized bodily infection or disease.