focus-, foci-

(Latin: hearth, fireplace; fire, flame; central point, center)

The word "focus" was introduced into mathematics by Johannes Kepler in 1604 with the meaning of any "central point".

omnifocal lens (s) (noun), omnifocal lenses (pl)
1. A lens for near and distant vision in which the reading portion is a continuously variable curve.
2. A lens whose power increases continuously and regularly in a downward direction, avoiding the discontinuity of bifocal and trifocal lenses.
Pro aris, Pro focis. (Latin terms)
Translation: "For the altar. For the hearth."

Also "For the altar (church or religion), For the hearth (home)."

refocus (verb), refocused, refocusing
1. To change or to adjust the focus of something; such as, a camera or a telescope.
2. To concentrate attention or efforts on something different.
trifocal (noun), trifocals (pl)
1. Having three focal lengths.
2. Having one section that corrects for distant vision, a second section that corrects for medium vision, and a third that corrects for near vision; such as, an eyeglass lens.
trifocal lens (s) (noun), trifocal lenses (pl)
A lens with three parts of different refracting powers: the upper for distant sights, the middle for intermediate views, and the lower for near visions.
unfocused, unfocussed (s) (noun); unfocuseds, unfocusseds
1. Something that is not adjusted for a clear image.
2. That which is lacking a clear purpose or objective.
3. Anything that is not centered on any specific thing or person.

Cross references of word groups that are related, directly, indirectly, or partly to: "fire, burn, glow, or ashes": ars-, ard-; -bust; cand-, cend-; caust-, caut-; crema-; ciner-; ether-; flagr-; flam-; fulg-; gehenna-; ign-; phleg-; phlog-; pyreto-, -pyrexia; pyr-; spod- (ashes; waste); volcan-.