focus

[ foh-kuhs ]

noun

, plural fo·cus·es or (especially British) fo·cus·ses, fo·ci [foh, -sahy, -kahy].

1. a central point, as of attraction, attention, or activity:

   The need to prevent a nuclear war became the focus of all diplomatic efforts.

   Synonyms: nucleus, core, heart, center

2. close attention or concentration:

   Some of the warning signs indicating you should pull over: drifting between lanes, repeated yawning, tailgating, and trouble maintaining focus.

3. the ability to concentrate one’s attention or to sustain concentration:

   Mindfulness and meditation are often suggested to help manage stress, increase awareness of emotions, and improve focus.

4. Physics. a point at which rays of light, heat, or other radiation meet after being refracted or reflected.
5. Optics.
   1. the focal point of a lens, on which rays converge or from which they deviate.
   2. the focal length of a lens; the distance from a focal point to a corresponding principal plane.
   3. the clear and sharply defined condition of an image.
   4. the position of a viewed object or the adjustment of an optical device necessary to produce a clear image:

      in focus; out of focus.

6. 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.
7. Geology. the point of origin of an earthquake.
8. Pathology. the primary center from which a disease develops or in which it localizes.

verb (used with object)

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

1. to bring to a focus or into focus; cause to converge on a perceived point:

   to focus the lens of a camera.

2. to concentrate:

   to focus one's thoughts;

   to focus troop deployment in the east.

verb (used without object)

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

1. to be or become focused:

   My eyes have trouble focusing on distant objects.

2. to direct one's attention or efforts:

   Students must focus in class.

focus

/ ˈfəʊkəs /

noun

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. another name for focal point 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. the point beneath the earth's surface at which an earthquake or underground nuclear explosion originates Compare epicentre
7. pathol the main site of an infection or a localized region of diseased tissue

verb

1. to bring or come to a focus or into focus
2. troften foll byon to fix attention (on); concentrate

focus

/ fō′kəs /

, or foci fō′sī′,fō′kī′

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

Derived Forms

• ˈfocuser, noun
• ˈfocusable, adjective

Other Words From

• fo·cus·a·ble adjective
• fo·cus·er noun
• mis·fo·cus verb misfocused misfocusing or (especially British) misfocussed misfocussing
• mis·fo·cused adjective
• mis·fo·cussed adjective
• o·ver·fo·cus verb (used with object) overfocused overfocusing or (especially British) overfocussed overfocussing
• re·fo·cus verb refocused refocusing or (especially British) refocussed refocussing
• self-fo·cused especially British, self-fo·cussed adjective
• self-fo·cus·ing especially British, self-fo·cus·sing adjective
• un·fo·cus·ing especially British, un·fo·cus·sing adjective
• well-fo·cused especially British, well-fo·cussed adjective

Word History and Origins

Origin of focus¹

First recorded in 1635–45; Latin: “fireplace, hearth”

Word History and Origins

Origin of focus¹

C17: via New Latin from Latin: hearth, fireplace

Example Sentences

A key Los Angeles City Council committee signed off on a sweeping rezoning plan Tuesday that would focus new market rate and affordable housing on commercial corridors and in existing dense residential neighborhoods.

From Los Angeles Times

This refrain underscores the growing partisan divide over the legislation’s priorities, with Republicans increasingly pushing for a focus on agriculture and rural development, while Democrats emphasize addressing food insecurity and expanding nutrition assistance programs.

From Salon

To achieve these improvements, the research team focused on understanding the efficiency and stability losses induced by the hole transport layer which plays an important role in the solar cell performance.

From Science Daily

This definition not only ignores cerebral palsy as a lifelong condition but contributes to a lopsided research focus directed only at pediatric care and not care into adulthood and across the lifespan, experts say.

From Science Daily

The carmaker is attempting to move away from its past as a mass-manufacturer of cheap "runabouts", and position itself as more upmarket brand, focused on electric cars.

From BBC

Related Words

• apply oneself to
• attend (to)
• concentrate
• engage
• fixate
• pay attention to
• pore over

What Is The Plural Of Focus?

Plural word for focus

The plural form of focus can be either focuses, focusses, or foci (pronounced [ foh-sahy] or [ foh-kahy ]). Focuses is the most commonly used plural form in nontechnical contexts in American English, while focuses is the most common in nontechnical contexts in British English. The plural foci is typically found only in technical contexts, as in physics, optics, or geometry. 

The plurals of several other singular words that end in -us are formed in the same way as foci, including fungus/fungi or cactus/cacti. 

Irregular plurals that are formed like foci derive directly from their original pluralization in Latin.

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.

Dig deeper

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?