Meaning of FOCAL in English

adj. of, at, or in terms of a focus. focal distance (or length) the distance between the centre of a mirror or lens and its focus. focal plane the plane through the focus perpendicular to the axis of a mirror or lens. focal point = FOCUS n. 1.

[ mod.L focalis (as FOCUS) ]

Concise Oxford English dictionary.      Краткий оксфордский словарь английского языка.