Also called principal focus. Optics. either of two points on the axis of a mirror, lens, or other optical system, one point being such that rays diverging from it are deviated parallel to the axis upon refraction or reflection by the system and the other point being such that rays parallel to the axis of the system converge to the point upon refraction or reflection by the system.
the point at which all elements or aspects converge; center of activity or attention:
The focal point of our discussion was the need for action.
the central or principal point of focus.
Also called principal focus, focus. the point on the axis of a lens or mirror to which parallel rays of light converge or from which they appear to diverge after refraction or reflection
a central point of attention or interest
focal point n.
The point at which all radiation coming from a single direction and passing through a lens or striking a mirror converges. Also called focus.
noun, Optics, Photography. 1. . noun 1. (photog) another name for f-number
- Focal reaction
focal reaction n. A limited reaction that occurs at the point of entrance of an infecting organism or of an injection. Also called local reaction.
- Focal segmental glomerulosclerosis
focal segmental glomerulosclerosis n. Segmental collapse of glomerular capillaries with thickened basement membranes and increased mesangial matrix, seen sometimes in nephrotic syndrome or mesangial proliferative glomerulonephritis.
noun, Pathology. 1. an epileptic manifestation arising from a localized anomaly in the brain, as a small tumor or scar, and usually involving a single motor or sensory mechanism but occasionally spreading to other areas and causing convulsions and loss of consciousness.