All 4 Uses

focus
in
Hatchet, by Gary Paulsen
(Edited)

One of the pilots had used a watch crystal as a magnifying glass to focus the sun and start a fire so they didn't have to eat the lizards raw.
p. 56.6 *

focus = concentrate at one spot
He shook his head, tried to focus his thoughts.
p. 85.8 *

focus = concentrate
So he went down to the side of the water and looked at the plane and focused his mind, the way he did when he was hunting the foolbirds and wanted to concentrate,
p. 149.9

focused = concentrated
...focused it on the pilot and thought: Have rest. Have rest forever.
p. 149.9

focused = concentrated (his mind)

Definitions:

(1) (focus as in: Turn your focus to question #2.)
to direct attention or effort toward a single thing; or the ability to do so without getting distracted
(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.
(5) (meaning too rare to warrant focus)