a. [ Cf. F. focal. See Focus. ] Belonging to, or concerning, a focus; as, a focal point. [ 1913 Webster ]
Focal distance, or length, of a lens or mirror (Opt.),
Focal distance of a telescope,
n. The act of focalizing or bringing to a focus, or the state of being focalized. [ 1913 Webster ]
v. t.
Light is focalized in the eye, sound in the ear. De Quincey. [ 1913 Webster ]