All 6 Uses of

focus
in
For Whom the Bell Tolls

He was walking beside her but his mind was thinking of the problem of the bridge now and it was all clear and hard and sharp as when a camera lens is brought into focus.
Chpt 13 *

focus = a state where something has come into view or can be seen clearly

He sat there, his moustache and his eyes focused on the map, on the map that he never truly understood, on the brown tracing of the contours that were traced fine and concentric as a spider's web.
Chpt 42 *

focused = looked

It was as though a reflex lens camera had been suddenly brought into focus.
Chpt 43

focus = a state where something has come into view or can be seen clearly

Definitions:

(1) (focus as in: Turn your focus to question #2.)
verb: to concentrate, look at, or pay attention to

noun: the act of concentration, or the ability to concentrate

(to concentrate is to direct attention or effort towards a single thing)
(2) (focus as in: The focus of our study is...)
where attention is concentrated or directed
(3) (focus as in: bring into focus; or out of focus)
a state where something has come into view or can be seen clearly; or an adjustment made to permit a clear view
(4) (focus as with technical usage)
technical usage typically involves some sense of center or concentration such as:
- physics — a point where things come together such as the point where light rays meet
- geometry — a fixed reference point (as of a parabola)
- geology — the point of origin of an earthquake
See a comprehensive dictionary for other less common meanings.