[ foh-kuhs ]
/ 藞fo蕣 k蓹s /
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See synonyms for: focus / foci / focused / focuses on Thesaurus.com

noun, plural fo路cus路es or (especially British) fo路cus路ses, fo路ci [foh-sahy, -kahy]. /藞fo蕣 sa瑟, -ka瑟/.
verb (used with object), fo路cused, fo路cus路ing or (especially British) fo路cussed, fo路cus路sing.
to bring to a focus or into focus; cause to converge on a perceived point: to focus the lens of a camera.
to concentrate: to focus one's thoughts;to focus troop deployment in the east.
verb (used without object), fo路cused, fo路cus路ing or (especially British) fo路cussed, fo路cus路sing.
to be or become focused: My eyes have trouble focusing on distant objects.
to direct one's attention or efforts: Students must focus in class.
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Origin of focus

First recorded in 1635鈥45; Latin: 鈥渇ireplace, hearth鈥


Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, 漏 Random House, Inc. 2023


Where does聽focus come from?

What does the word focus bring to your mind? Maybe you think of a photograph that is clear and sharply defined. Or perhaps you recall a teacher tsk-tsking you to pay attention in class. But what about a fireplace?

Well, the word focus comes directly from the Latin focus, which meant 鈥渇ireplace鈥 or 鈥渉earth鈥 (that is, the floor of a fireplace). This is what focus originally meant in English when the word entered the language around 1635鈥45, though that sense has been extinguished, as it were.

But the word focus burned on in other ways. As the 1600s unfolded, focus was given new meanings in the great scientific literature of that age, which were largely written in what鈥檚 known as New Latin. In the 1650s, the influential English philosopher and author Thomas Hobbes used focus for a kind of fixed point in geometry. So did Isaac Newton鈥攜ou know, of gravity fame鈥攊n the 1690s.

Other applications of the word focus in the late 1600s came about in the fields of medicine and physics. In physics, a focus is 鈥渁 point at which rays of light, heat, or other radiation meet after being refracted or reflected.鈥 Perhaps you can imagine how a fireplace or a hearth鈥攃ontained areas and sources of heat and light鈥攚as likened to such a point in math and science.

Dig deeper

The word focus took on a number of senses in optics, specifically 鈥渢he point on a lens on which rays converge or from which they deviate.鈥 A more familiar sense of focus is 鈥渢he clear and sharply defined condition of an image,鈥 as when the image isn鈥檛 blurry. Optics has also given us the expressions in focus and out of focus, which can be used both literally and figuratively.

From these various ideas of clarity and convergence in optics arises one of the more common, everyday ways we use the word focus today: 鈥渁 central point, as a of attention, activity, or activity.鈥 For example, Finding a cure for cancer was the focus of his long career. Focus also refers to ability to concentrate, as in The teacher felt the students struggled with their focus. These senses of focus had spread by the early 1800s, around when various verb forms of focus take off. The adjective form of focus is focal.

Did you know ... ?

The Latin word focus became the general word for 鈥渇ire鈥 in the language鈥檚 descendants. Spanish fuego, French fue, Italian fuoco, Portuguese fogo, Romanian foco, to cite just the most spoken Romance languages鈥攁ll of these words for 鈥渇ire鈥 come from the Latin focus.

So does another French word for a different part of the house: the foyer. A foyer refers to a lobby of a theater, hotel, or apartment house. In French, a foyer was originally a room to which theater audiences went for warmth between the acts.

There鈥檚 just something about a fireplace, isn鈥檛 there? Its magic wasn鈥檛 lost on the ancient Romans, either: focus was also extended to mean 鈥渉ome, family,鈥 a metaphor also at work in English鈥檚 very own word hearth. Now that warms the heart, doesn鈥檛 it?

How to use focus in a sentence

British Dictionary definitions for focus

/ (藞f蓹蕣k蓹s) /

noun plural -cuses or -ci (-sa瑟, -ka瑟, -ki藧)
verb -cuses, -cusing, -cused, -cusses, -cussing or -cussed
to bring or come to a focus or into focus
(tr often foll by on) to fix attention (on); concentrate

Derived forms of focus

focusable, adjectivefocuser, noun

Word Origin for focus

C17: via New Latin from Latin: hearth, fireplace
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition 漏 William Collins Sons & Co. Ltd. 1979, 1986 漏 HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for focus

[ f艒k蓹s ]

Plural focuses or foci (f艒s墨鈥, f艒k墨鈥)
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.
The American Heritage庐 Science Dictionary Copyright 漏 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.