focus Meaning, Definition & Usage

  1. noun the concentration of attention or energy on something
    direction; centering; focussing; focal point; focusing.
    • the focus of activity shifted to molecular biology
    • he had no direction in his life
  2. noun maximum clarity or distinctness of an image rendered by an optical system
    • in focus
    • out of focus
  3. noun maximum clarity or distinctness of an idea
    • the controversy brought clearly into focus an important difference of opinion
  4. noun a central point or locus of an infection in an organism
    nidus; focal point.
    • the focus of infection
  5. noun special emphasis attached to something
    stress.
    • the stress was more on accuracy than on speed
  6. noun a point of convergence of light (or other radiation) or a point from which it diverges
    focal point.
  7. noun a fixed reference point on the concave side of a conic section
  8. verb direct one's attention on something
    center; centre; pore; concentrate; rivet.
    • Please focus on your studies and not on your hobbies
  9. verb cause to converge on or toward a central point
    • Focus the light on this image
  10. verb bring into focus or alignment; to converge or cause to converge; of ideas or emotions
    focalise; focalize; concentre; concenter.
  11. verb become focussed or come into focus
    focalize; focalise.
    • The light focused
  12. verb put (an image) into focus; we cannot enjoy the movie"
    sharpen; focalize; focalise.
    • Please focus the image

WordNet

Fo"cus noun
Etymology
L. focus hearth, fireplace; perh. akin to E. bake. Cf. Curfew, Fuel, Fusil the firearm.
Wordforms
plural E Focuses L Foci
Definitions
  1. (Opt.) A point in which the rays of light meet, after being reflected or refrcted, and at which the image is formed; as, the focus of a lens or mirror.
  2. (Geom.) A point so related to a conic section and certain straight line called the directrix that the ratio of the distace between any point of the curve and the focus to the distance of the same point from the directrix is constant. ✍ Thus, in the ellipse FGHKLM, A is the focus and CD the directrix, when the ratios FA:FE, GA:GD, MA:MC, etc., are all equal. So in the hyperbola, A is the focus and CD the directrix when the ratio HA:HK is constant for all points of the curve; and in the parabola, A is the focus and CD the directrix when the ratio BA:BC is constant. In the ellipse this ratio is less than unity, in the parabola equal to unity, and in the hyperbola greater than unity. The ellipse and hyperbola have each two foci, and two corresponding directrixes, and the parabola has one focus and one directrix. In the ellipse the sum of the two lines from any point of the curve to the two foci is constant; that is: AG+GB=AH+HB; and in the hyperbola the difference of the corresponding lines is constant. The diameter which passes through the foci of the ellipse is the major axis. The diameter which being produced passes through the foci of the hyperbola is the transverse axis. The middle point of the major or the transverse axis is the center of the curve. Certain other curves, as the lemniscate and the Cartesian ovals, have points called foci, possessing properties similar to those of the foci of conic sections. In an ellipse, rays of light coming from one focus, and reflected from the curve, proceed in lines directed toward the other; in an hyperbola, in lines directed from the other; in a parabola, rays from the focus, after reflection at the curve, proceed in lines parallel to the axis. Thus rays from A in the ellipse are reflected to B; rays from A in the hyperbola are reflected toward L and M away from B.
  3. A central point; a point of concentration.
Fo"cus transitive verb
Wordforms
imperfect & past participle Focused ; present participle & verbal noun Focusing
Definitions
  1. To bring to a focus; to focalize; as, to focus a camera. R. Hunt.

Webster 1913