noun, plural fo·cus·es, fo·ci [foh-sahy, -kahy] /ˈfoʊ saɪ, -kaɪ/.
- 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.
verb (used with object), fo·cused, fo·cus·ing or (especially British) fo·cussed, fo·cus·sing.
verb (used without object), fo·cused, fo·cus·ing or (especially British) fo·cussed, fo·cus·sing.
Origin of focus
OTHER WORDS FROM focus
Words nearby focus
BEHIND THE WORD
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?
Example sentences from the Web for focus
Stephanie Giorgio, a classical musician, credits The Class for helping her cope with anxiety, focus, fear, and self-doubt.How Taryn Toomey’s ‘The Class’ Became New York’s Latest Fitness Craze |Lizzie Crocker |January 9, 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
The focus here was on how fast oil would come out of the Canadian fields.
Investigators will focus on whether the sudden emergency was so extreme that no degree of pilot skill would have helped.Flight 8501 Poses Question: Are Modern Jets Too Automated to Fly? |Clive Irving |January 4, 2015 |DAILY BEAST
The silence seemed to focus itself upon the cook, who fumbled at his coat collar and cleared his voice.Hilda |Sarah Jeanette Duncan
Of course, the real force of the aim lies in its serving as the focus of thought.Principles of Teaching |Adam S. Bennion
The constitution of the language is the result of the change of focus from signs to relations among them.The Civilization of Illiteracy |Mihai Nadin
Each of the points was the focus of frightful and singular pangs.Sea Stories |Various
The little spruce leaped out clear and distinct as he got the focus.The Boy Scouts in A Trapper's Camp |Thornton W. Burgess