Borrowed from Latin focus (“hearth, fireplace”); see there for more. Related to fuel.
Kepler introduced the term into mathematics and the sciences in describing elliptical orbits of planets (quote from Nicholas Mee):
"One of the interesting properties of an ellipse is that if there were a light bulb at one focus, then all the light that it emits would reflect off the ellipse and converge at the other focus. This is why Kepler originally used the name focus for these points."
Meanings
(countable) A point at which reflected or refracted rays of light converge.
The heat of sunlight at the focus of a magnifying glass can easily set dry leaves on fire.
(countable) A point of a conic at which rays reflected from a curve or surface converge.
(uncountable) The fact of the convergence of light on the photographic medium.
Unfortunately, the license plate is out of focus in this image.
Not long ago, it was difficult to produce photographs of tiny creatures with every part in focus.[…]A photo processing technique called focus stacking has changed that. Developed as a tool to electronically combine the sharpest bits of multiple digital images, focus stacking is a boon to biologists seeking full focus on a micron scale. 2013 July-August, Catherine Clabby, “Focus on Everything”, in American Scientist:
(uncountable) The quality of the convergence of light on the photographic medium.
During this scene, the boy’s face shifts subtly from soft focus into sharp focus.
(uncountable) Concentration of attention.
I believe I can bring the high degree of focus required for this important job.
(countable) Something to which activity, attention or interest is primarily directed.
My studies are my main focus right now.
(countable) The exact point of where an earthquake occurs, in three dimensions (underneath the epicentre).
The earthquake's focus was at exactly 37 degrees north, 18 degrees south, seventy five meters below the ground.
(countable, uncountable) The status of being the currently active element in a user interface, often indicated by a visual highlight.
Text entered at the keyboard or pasted from a clipboard is sent to the component which currently has the focus.
(countable, uncountable) The most important word or phrase in a sentence or passage, or the one that imparts information.
(countable, uncountable) An object used in casting a magic spell.
Candles, in fact, are an essential ingredient in many spells. They can be used as either the focus of the spell or as a component that sets the spell's overall mood and tone. 2004, Marian Singer, Trish MacGregor, The Only Wiccan Spell Book You'll Ever Need:
(countable, uncountable) The centre of an older fish's scale, which is the point where a younger fish's scale starts to grow from.
da fokus (in mathematics) · de Fokus (quality of the convergence of light on the photographic medium) · fi fokus (in optics) · id fokus (concentration of attention) · et fookus (in optics) · nl brandpunt (fact of the convergence of light on the photographic medium) · cmn 集中 (concentration of attention) · et fookus (quality of the convergence of light on the photographic medium) · vi tính rõ nét (quality of the convergence of light on the photographic medium) · bg фокус (in optics) · kmr tîşko (quality of the convergence of light on the photographic medium) · es foco (concentration of attention) · nl brandpunt (in mathematics) · mk фокус (in mathematics) · ga fócas (concentration of attention) · fi polttopiste (in optics) · et fookus (in mathematics) · hu gyújtópont (in optics) · de Fokus (fact of the convergence of light on the photographic medium) · vi trọng tâm (concentration of attention) · ja 集中 (concentration of attention) · es foco (in mathematics) · mi aronga (concentration of attention) · fi tarkennus (quality of the convergence of light on the photographic medium) · nl focus (concentration of attention) · de Fokus (in optics) · eo fokuso (concentration of attention) · ar بُؤْرَة (concentration of attention) · nn fokus (concentration of attention) · id titik api (in optics) · da fokus (fact of the convergence of light on the photographic medium) · pt foco (in optics) · fi keskittyminen (concentration of attention) · ko 초점 (in mathematics) · fr foyer (in mathematics) · fi leikkauspiste (in mathematics) · pt foco (quality of the convergence of light on the photographic medium) · ga fócas (in mathematics) · da fokus (concentration of attention) · mi ngahunga (in mathematics) · ga fócas (fact of the convergence of light on the photographic medium) · fa تمرکز (concentration of attention) · ca focus (in mathematics) · fr foyer (in optics) · ja ピント (quality of the convergence of light on the photographic medium) · id pumpunan (in optics) · da fokus (in optics) · ru фока́льная то́чка (in mathematics) · vi tiêu điểm (fact of the convergence of light on the photographic medium) · ko 집중 (concentration of attention) · pl koncentracja (concentration of attention) · ga fócas (in optics) · nb fokus (concentration of attention) · sv fokus (quality of the convergence of light on the photographic medium) · fi tarkennus (fact of the convergence of light on the photographic medium) · sv fokus (fact of the convergence of light on the photographic medium) · es enfoque (quality of the convergence of light on the photographic medium) · vi tiêu điểm (in mathematics) · nl brandpunt (in optics) · pt foco (in mathematics) · ru наво́дка на ре́зкость (quality of the convergence of light on the photographic medium) · ja 焦点 (in optics) · tl katumbukan (in mathematics) · sv brännpunkt (in optics) · sv skärpa (quality of the convergence of light on the photographic medium) · hu fókusz (in optics) · de Konzentration (concentration of attention) · es punto focal (in optics) · de Brennpunkt (in mathematics) · fa کانون (in optics) · mi ngahunga (in optics) · it fuoco (in optics) · hi ध्यान (concentration of attention) · nn fokus (in optics) · fa فوکوس (in optics) · ru средото́чие (concentration of attention) · fi polttopiste (in mathematics) · bg фокус (in mathematics) · pt enfoque (concentration of attention) · vi tiêu điểm (in optics) · sv fokus (concentration of attention) · nb brennpunkt (in optics) · ru сосредото́чение (concentration of attention) · ga fócas (quality of the convergence of light on the photographic medium) · tl katumbukan (in optics) · nb fokus (in optics) · ru фо́кус (in optics) · ru концентра́ция внима́ния (concentration of attention) · it fuoco (in mathematics) · ro concentrare (concentration of attention) · hu fókusz (fact of the convergence of light on the photographic medium) · eo fokuso (in optics) · de Brennpunkt (in optics) · da fokus (quality of the convergence of light on the photographic medium) · hy կիզակետ (in optics) · ca focus (concentration of attention) · ko 초점 (in optics) · om hubannaa (concentration of attention) · ga príomhchúram (concentration of attention) · id titik api (in mathematics) · sv fokus (in optics) · pt foco (concentration of attention) · ru фо́кус (in mathematics) · sv skärpa (fact of the convergence of light on the photographic medium) · nl focus (in mathematics) · tr odak (in optics) · nl brandpunt (quality of the convergence of light on the photographic medium) · mg fifantohana (concentration of attention) · cmn 焦點 /焦点 (in optics) · ru концентра́ция (concentration of attention) · es enfoque (fact of the convergence of light on the photographic medium) · eo atento (concentration of attention) · ja 焦点 (in mathematics) · et fookus (fact of the convergence of light on the photographic medium) · pl ognisko (in optics) · pt concentração (concentration of attention) · et keskendus (concentration of attention) · bg фокус (quality of the convergence of light on the photographic medium) · nn brennpunkt (in optics) · id pumpunan (concentration of attention) · pt enfoque (fact of the convergence of light on the photographic medium) · cs ohnisko (in optics) · nl focus (in optics) · fr attention (concentration of attention) · es foco (in optics) · mk фокус (in optics) · ca focus (in optics) · kmr tîşko (in optics) · ru фока́льная то́чка (in optics)
Borrowed from Latin focus (“hearth, fireplace”); see there for more. Related to fuel.
Kepler introduced the term into mathematics and the sciences in describing elliptical orbits of planets (quote from Nicholas Mee):
"One of the interesting properties of an ellipse is that if there were a light bulb at one focus, then all the light that it emits would reflect off the ellipse and converge at the other focus. This is why Kepler originally used the name focus for these points."
Meanings
(transitive) To cause (rays of light, etc) to converge at a single point.
The difficulties of focussing colour-light signals on curved tracks to ensure maximum sighting distance were underlined in the recent official report [...] on a low-speed collision at Newcastle Central on July 25, 1960, between an unfitted freight and a diesel-hauled passenger train. 1961 February, “Talking of Trains: Collision at Newcastle”, in Trains Illustrated, pages 75–76:
(transitive) To adjust (a lens, an optical instrument) in order to position an image with respect to the focal plane.
You'll need to focus the microscope carefully in order to capture the full detail of this surface.
(intransitive, of a lens, qualifier:optical instrument, usually) To adjust itself or be adjusted such that light from a scene converges appropriately to create a clear image.
I can't get the lens to focus.
The camera focuses automatically on the subject's eyes.
(transitive) To direct attention, effort, or energy to a particular audience or task.
The president focused her remarks on the newcomers.
(intransitive) To concentrate one’s attention.
If you're going to beat your competitors, you need to focus.
(followed by on or upon, intransitive) To concentrate one's attention on something; to have as one's central point of interest, concern, etc.
I have to focus on my work.
(transitive) To transfer the input focus to (a visual element), so that it receives subsequent input.
The text box won't receive the user's keystrokes unless you explicitly focus it.
(qualifier:formerly) To aggregate figures of accounts.
Whole pages of it are filled with masses of figures, generally single numbers added up in batches, and then the totals added in batches again, as though he were "focusing" some account, as the auditors put it. 1897, Bram Stoker, Dracula, published 1993, page 67:
fi kiinnittää huomionsa ((intransitive) to concentrate one's attention on something) · sv koncentrera sig ((intransitive) to concentrate one's attention) · hu élesre állít ((transitive, optics) to adjust (a lens, an optical instrument)) · uk зосередитися ((intransitive) to concentrate one's attention) · pt focar-se ((intransitive) to concentrate one's attention) · pl skupić się ((intransitive) to concentrate one's attention) · ga fócasaigh ((transitive, optics) to adjust (a lens, an optical instrument)) · es centrarse en ((intransitive) to concentrate one's attention on something) · fr se concentrer ((intransitive) to concentrate one's attention on something) · uk сфокусува́ти (to cause (rays of light, etc) to converge at a single point) · ja 集中する ((intransitive) to concentrate one's attention) · el εστιάζω (to cause (rays of light, etc) to converge at a single point) · sv ställa in skärpan ((transitive, optics) to adjust (a lens, an optical instrument)) · ro focaliza ((transitive, optics) to adjust (a lens, an optical instrument)) · fr focaliser (to cause (rays of light, etc) to converge at a single point) · ru сфокуси́ровать ((transitive, optics) to adjust (a lens, an optical instrument)) · uk сфокусува́ти ((transitive, optics) to adjust (a lens, an optical instrument)) · fr concentrer ((transitive) To direct (attention, effort, or energy to)) · de sich konzentrieren ((intransitive) to concentrate one's attention on something) · ru концентри́ровать ((intransitive) to concentrate one's attention on something) · nl focussen ((intransitive) to concentrate one's attention) · bg съсредоточавам се ((intransitive) to concentrate one's attention on something) · vi đưa tiêu điểm ((computing, graphical user interface) to transfer the input focus to) · uk сфокусува́тися ((intransitive, optics) To adjust itself or be adjusted such that light from a scene converges appropriately) · es afocar ((transitive, optics) to adjust (a lens, an optical instrument)) · it mettere a fuoco ((transitive, optics) to adjust (a lens, an optical instrument)) · fi tarkentaa ((transitive, optics) to adjust (a lens, an optical instrument)) · be засяродзіцца ((intransitive) to concentrate one's attention) · ca enfocar ((intransitive) to concentrate one's attention on something) · bg фокусирам (to cause (rays of light, etc) to converge at a single point) · da koncentrere sig ((intransitive) to concentrate one's attention) · it focalizzare (to cause (rays of light, etc) to converge at a single point) · es enfocar (to cause (rays of light, etc) to converge at a single point) · ru наводить на фокус ((transitive, optics) to adjust (a lens, an optical instrument)) · mi whakaarorangi ((intransitive) to concentrate one's attention) · el εστιάζω ((transitive) To direct (attention, effort, or energy to)) · ru сосредото́чиваться ((intransitive) to concentrate one's attention) · la animadverto ((intransitive) to concentrate one's attention) · pt focalizar ((transitive, optics) to adjust (a lens, an optical instrument)) · hu összpontosít ((intransitive) to concentrate one's attention on something) · ru фокуси́ровать ((transitive, optics) to adjust (a lens, an optical instrument)) · vi tập trung ((intransitive) to concentrate one's attention) · mk концентри́ра ((intransitive) to concentrate one's attention on something) · ru сосредото́чивать ((intransitive) to concentrate one's attention on something) · it concentrarsi ((intransitive) to concentrate one's attention on something) · ca enfocar ((transitive, optics) to adjust (a lens, an optical instrument)) · be засяроджвацца ((intransitive) to concentrate one's attention) · vi tập trung ((intransitive) to concentrate one's attention on something) · la animadverto ((intransitive) to concentrate one's attention on something) · da koncentrere sig om ((intransitive) to concentrate one's attention on something) · de fokussieren ((intransitive) to concentrate one's attention on something) · pt focar ((intransitive) to concentrate one's attention on something) · ro se concentra (on/upon: pe/asupra) ((intransitive) to concentrate one's attention on something) · ca enfocar (to cause (rays of light, etc) to converge at a single point) · hu koncentrál ((intransitive) to concentrate one's attention) · es concentrarse ((intransitive) to concentrate one's attention) · es enfocar ((intransitive) to concentrate one's attention on something) · de sich konzentrieren ((intransitive) to concentrate one's attention) · ru фокуси́роваться ((intransitive, optics) To adjust itself or be adjusted such that light from a scene converges appropriately) · uk фокусува́тися ((intransitive, optics) To adjust itself or be adjusted such that light from a scene converges appropriately) · io enfokigar (to cause (rays of light, etc) to converge at a single point) · ko 집중하다 ((intransitive) to concentrate one's attention) · vi làm tụ vào (to cause (rays of light, etc) to converge at a single point) · ru сфокуси́роваться ((intransitive, optics) To adjust itself or be adjusted such that light from a scene converges appropriately) · nl zich concentreren ((intransitive) to concentrate one's attention) · eo enfokusigi ((transitive, optics) to adjust (a lens, an optical instrument)) · fi kohdistaa (to cause (rays of light, etc) to converge at a single point) · fr se concentrer ((intransitive) to concentrate one's attention) · ja 絞る (to cause (rays of light, etc) to converge at a single point) · cmn 集中 ((intransitive) to concentrate one's attention) · tr odaklanmak ((intransitive) to concentrate one's attention on something) · uk фокусува́ти (to cause (rays of light, etc) to converge at a single point) · el εστιάζω ((transitive, optics) to adjust (a lens, an optical instrument)) · vi điều chỉnh tiêu điểm ((transitive, optics) to adjust (a lens, an optical instrument)) · ja 集中する ((intransitive) to concentrate one's attention on something) · ga fócasaigh (to cause (rays of light, etc) to converge at a single point) · es enfocar ((transitive, optics) to adjust (a lens, an optical instrument)) · nn fokusere ((intransitive) to concentrate one's attention) · mi whakanga(nga)hu ((transitive, optics) to adjust (a lens, an optical instrument)) · uk фокусува́ти ((transitive, optics) to adjust (a lens, an optical instrument)) · da fokusere på ((intransitive) to concentrate one's attention on something) · mk сосредоточува ((intransitive) to concentrate one's attention on something) · ru сосредото́чить ((intransitive) to concentrate one's attention on something) · pl skoncentrować się ((intransitive) to concentrate one's attention) · hu fókuszba állít ((transitive, optics) to adjust (a lens, an optical instrument)) · sv fokusera ((intransitive) to concentrate one's attention) · nb fokusere ((intransitive) to concentrate one's attention) · pt focalizar (to cause (rays of light, etc) to converge at a single point) · ru сконцентри́ровать ((intransitive) to concentrate one's attention on something) · nl zich focussen ((intransitive) to concentrate one's attention) · ru концентри́роваться ((intransitive) to concentrate one's attention) · bg фокусирам ((transitive, optics) to adjust (a lens, an optical instrument)) · vi đặt tiêu điểm ((computing, graphical user interface) to transfer the input focus to) · ga dírigh ar ((intransitive) to concentrate one's attention) · da fokusere ((transitive, optics) to adjust (a lens, an optical instrument)) · hu fókuszál ((intransitive) to concentrate one's attention on something) · de fokussieren ((transitive, optics) to adjust (a lens, an optical instrument)) · it concentrarsi ((intransitive) to concentrate one's attention) · hu fókuszál ((transitive, optics) to adjust (a lens, an optical instrument)) · nn fokusera ((intransitive) to concentrate one's attention) · ru сосредото́читься ((intransitive) to concentrate one's attention) · sv fokusera ((intransitive) to concentrate one's attention on something) · da fokusere ((intransitive) to concentrate one's attention) · io enfokigar ((transitive, optics) to adjust (a lens, an optical instrument)) · fi keskittää huomionsa ((intransitive) to concentrate one's attention on something) · de fokussieren (to cause (rays of light, etc) to converge at a single point) · fr mettre au point ((transitive, optics) to adjust (a lens, an optical instrument)) · uk зосереджуватися ((intransitive) to concentrate one's attention) · ro focaliza (to cause (rays of light, etc) to converge at a single point) · fi keskittyä ((intransitive) to concentrate one's attention on something) · sv fokusera ((transitive, optics) to adjust (a lens, an optical instrument)) · fr se focaliser ((intransitive) to concentrate one's attention) · ro se concentra ((intransitive) to concentrate one's attention) · sv ställa in fokus ((transitive, optics) to adjust (a lens, an optical instrument)) · pl skupiać (to cause (rays of light, etc) to converge at a single point) · bg концентрирам се ((intransitive) to concentrate one's attention on something) · is einbeita ((intransitive) to concentrate one's attention) · pl skupiać się ((intransitive) to concentrate one's attention) · fi kohdistaa ((computing, graphical user interface) to transfer the input focus to) · hu koncentrál ((intransitive) to concentrate one's attention on something) · hu összpontosít ((intransitive) to concentrate one's attention) · ja ピントを合わせる ((transitive, optics) to adjust (a lens, an optical instrument)) · fi keskittyä ((intransitive) to concentrate one's attention) · ru сконцентри́роваться ((intransitive) to concentrate one's attention)