1 Likewise, at two years of age a cat has reached the same maturity as a person of 25 years, so the second year of a cat's life is equivalent to 10 years (25 minus 15) of a person's. 2  Thereafter, each calendar year a cat ages the equivalent of 4 human years.
countable noun. 1  The focal point of something is the thing that people concentrate on or pay most attention to. 2  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. 3  a central point of attention or interest.
The focal length of a lens is the distance from the center of the lens to the point at which it focuses light rays. The shorter the focal length, the more powerful the lens. (It's easy to see why: an ordinary piece of glass would be like a lens of infinite focal length and wouldn't bring light rays to a focus at all.