- 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
- The point at which all radiation coming from a single direction and passing through a lens or striking a mirror converges. Also called focus