polttopiste

Etymology
, from the fact that a convex lens concentrates the rays of the sun into the focus of the lens, which may cause a flammable material to catch fire.

Noun

 * 1)  focus point at which reflected or refracted rays of light converge
 * 2)  focus point of a conic at which rays reflected from a curve or surface converge
 * 1)  focus point of a conic at which rays reflected from a curve or surface converge