- the focal point of a lens, on which rays converge or from which they deviate.
- the focal length of a lens; the distance from a focal point to a corresponding principal plane.
- 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.
Origin of focus
OTHER WORDS FROM focus
Words nearby focus
MORE ABOUT FOCUS
Where does 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 “fireplace” or “hearth” (that is, the floor of a fireplace). This is what focus originally meant in English when the word entered the language around 1635–45, 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’s 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—you know, of gravity fame—in 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 “a point at which rays of light, heat, or other radiation meet after being refracted or reflected.” Perhaps you can imagine how a fireplace or a hearth—contained areas and sources of heat and light—was likened to such a point in math and science.
The word focus took on a number of senses in optics, specifically “the point on a lens on which rays converge or from which they deviate.” A more familiar sense of focus is “the clear and sharply defined condition of an image,” as when the image isn’t 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: “a central point, as a of attention, activity, or activity.” 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 “fire” in the language’s descendants. Spanish fuego, French fue, Italian fuoco, Portuguese fogo, Romanian foco, to cite just the most spoken Romance languages—all of these words for “fire” 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’s just something about a fireplace, isn’t there? Its magic wasn’t lost on the ancient Romans, either: focus was also extended to mean “home, family,” a metaphor also at work in English’s very own word hearth. Now that warms the heart, doesn’t it?
How to use focus in a sentence
In the intervening period, as we weighed the cost of our overall portfolio and strategic focus, we made the decision not to relaunch the service.
Several startups, including MJ Platform and BioTrack, are building similar platforms for this market, but Canix says the company’s focus on improving data entry makes it stand apart.Canix aims to ease cannabis cultivators’ regulatory bookkeeping|Matt Burns|September 17, 2020|TechCrunch
West Virginia environmental regulators are proposing to reduce the fines that a coal company owned by the state’s governor could pay for water pollution violations that are the focus of a federal court case.This Billionaire Governor’s Coal Company Might Get a Big Break From His Own Regulators|by Ken Ward Jr.|September 17, 2020|ProPublica
Initially there may be a limited supply of vaccines available, and the focus will be on protecting health workers, other essential employees, and people in vulnerable groups.U.S. outlines sweeping plan to provide free COVID-19 vaccines|Rachel Schallom|September 16, 2020|Fortune
However, different aspects vary based on the agency’s focus.How would an SEO agency be built today? Part 2: Current business model(s)|Sponsored Content: SEOmonitor|September 16, 2020|Search Engine Land
Back in New York, the slow pace and inward focus of her yoga practice was less fulfilling.
Stephanie Giorgio, a classical musician, credits The Class for helping her cope with anxiety, focus, fear, and self-doubt.
There is a particular focus in the magazine on attacking the United States, which al Qaeda calls a top target.U.S. Spies See Al Qaeda Fingerprints on Paris Massacre|Shane Harris, Nancy A. Youssef|January 8, 2015|DAILY BEAST
And too much of a focus on numbers can obscure strategic truths.Pentagon Doesn’t Know How Many People It’s Killed in the ISIS War|Nancy A. Youssef|January 7, 2015|DAILY BEAST
His wife passed away and they had kids, and he wanted to focus on being a dad so he just stopped to raise his kids.Coffee Talk with Fred Armisen: On ‘Portlandia,’ Meeting Obama, and Taylor Swift’s Greatness|Marlow Stern|January 7, 2015|DAILY BEAST
Lessard's high-handed squelching of MacRae had thrown everything out of focus.Raw Gold|Bertrand W. Sinclair
William Weedham brought scowling eyes to focus upon Kip Burland.
It is doubtful if any woman had done as much to entice them to a common focus as the surmounting Mrs. Hofer.Ancestors|Gertrude Atherton
Why the focus of the telescope should change during a long exposure is not quite clear.
Before beginning an exposure the focus is adjusted by means of a high-power positive eyepiece.