- A point at which rays of light or other radiation converge or from which they appear to diverge, as after refraction or reflection in an optical system: the focus of a lens. Also called focal point.
- See focal length.
- The distinctness or clarity of an image rendered by an optical system.
- The state of maximum distinctness or clarity of such an image: in focus; out of focus.
- An apparatus used to adjust the focal length of an optical system in order to make an image distinct or clear: a camera with automatic focus.
- A center of interest or activity. See synonyms at center.
- Close or narrow attention; concentration: "He was forever taken aback by (Anne Tyler).
- A condition in which something can be clearly apprehended or perceived: couldn't get the problem into focus.
- Pathology. The region of a localized bodily infection or disease.
- Geology. The point of origin of an earthquake.
- Mathematics. A fixed point whose relationship with a directrix determines a conic section.
v., -cused, or -cussed, -cus·ing, or -cus·sing, -cus·es, or -cus·ses. v.tr.
- To cause (light rays, for example) to converge on or toward a central point; concentrate.
- To render (an object or image) in clear outline or sharp detail by adjustment of one's vision or an optical device; bring into focus.
- To adjust (a lens, for example) to produce a clear image.
- To direct toward a particular point or purpose: focused all their attention on finding a solution to the problem.
- To converge on or toward a central point of focus; be focused.
- To adjust one's vision or an optical device so as to render a clear, distinct image.
- To concentrate attention or energy: a campaign that focused on economic issues.
[Latin, hearth.]
focuser fo'cus·er n.
