focus

Meanings

1. 1
   noun

   maximum clarity or distinctness of an image rendered by an optical system

   in focus

2. 2
   noun

   maximum clarity or distinctness of an idea

   the controversy brought clearly into focus an important difference of opinion

3. 3
   noun

   the concentration of attention or energy on something

   the focus of activity shifted to molecular biology

4. 4
   noun

   a central point or locus of an infection in an organism

   the focus of infection

5. 5
   verb

   put (an image) into focus

   Please focus the image

6. 6
   verb

   become focussed or come into focus

   The light focused

7. 7
   verb

   direct one's attention on something

   Please focus on your studies and not on your hobbies

8. 8
   noun

   A point at which reflected or refracted rays of light converge.

   The heat of sunlight at the focus of a magnifying glass can easily set dry leaves on fire.

Etymology

Borrowed from Latin focus (“hearth, fireplace”); see there for more. Related to fuel. Kepler introduced the term into mathematics and the sciences in describing elliptical orbits of planets (quote from Nicholas Mee) : "One of the interesting properties of an ellipse is that if there were a light bulb at one focus, then all the light that it emits would reflect off the ellipse and converge at the other focus. This is why Kepler originally used the name focus for these points."