foci Definition

focus
noun focuses, foci

1. The point at which rays of light or sound waves converge or appear to diverge.
2. optics.
focal point 1.
3a. The condition in which an image is sharp;

Example: The picture is in focus
3b. The state of an instrument producing this image.

Example: The telescope is in focus
Example: These binoculars are out of focus
4. geol.
In seismology: the location of the centre of an earthquake, where the subterranean fracture takes place and from which the elastic waves radiate outward. See also epicentre.
5. A centre of interest or attention.

Thesaurus: crux, centre, core, nucleus, hub, heart, axis, focal point, centre of attraction, linchpin, target, pivot.
6. Special attention paid to something.

Example: a shift of focus
7. pathol.
The main site of an infection.
8. geom.
A point associated with a conic section where the distance between it and any point on the curve is a fixed ratio (the eccentricity 4) to the distance between that point and a line (the directrix).

verb focused, focusing, focussed, focussing

tr & intr
1. To bring or be brought into focus; to meet or make something meet or converge at a focus.
2. To adjust the thickness of the lens of (the eye) or to move the lens of (an optical instrument) so as to obtain the sharpest possible image of a particular object.
3. To cause (electron beams) to converge or diverge by varying the voltage or current that controls the magnetic or electric fields through which they pass.
tr & intr
4. To concentrate (one's attention, etc) on it.

Example: focused her energies on the problem
Example: focused on the problem
Thesaurus: concentrate, zero in, home in, converge, spotlight, aim, centre, direct, rivet, fix.
Form: focus something on something (often)

Etymology: 17c: Latin, meaning ‘hearth or fireplace'; probably referring to the ‘burning point of a lens or mirror'.