You searched for: “foci
focus (s) (noun), foci (pl)
1. 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.
2. The distinctness or clarity of an image rendered by an optical system.
3. The state of maximum clarity of an image; such as, in focus or out of focus.
4. An apparatus used to adjust the focal length of an optical system in order to make an image distinct or clear; for an example, a camera with automatic focus.
5. A condition in which something can be clearly apprehended or perceived: Harry simply couldn't get the problem into focus.
6. In pathology, the region of a localized bodily infection or disease.
7. In geology, the point of origin of an earthquake.
8. Etymology: from New Latin, focus, "central point"; from Latin focus, "hearth, fireplace".

The New Latin use was introduced in a Latin text about astronomy in 1604 by the German astronomer and mathematician, Johann Kepler, with reference to the "burning point (at which heat rays meet) of a lens or mirror".

This entry is located in the following unit: focus-, foci- (page 1)
(Latin: hearth, fireplace; fire, flame; central point, center)