Definitions of focus:

• noun:   maximum clarity or distinctness of an image rendered by an optical system

  Example: "In focus"

• noun:   maximum clarity or distinctness of an idea

  Example: "The controversy brought clearly into focus an important difference of opinion"

• noun:   the concentration of attention or energy on something

  Example: "The focus of activity shifted to molecular biology"

• noun:   a fixed reference point on the concave side of a conic section
• noun:   a point of convergence of light (or other radiation) or a point from which it diverges
• noun:   a central point or locus of an infection in an organism

  Example: "The focus of infection"

• noun:   special emphasis attached to something
• verb:   cause to converge on or toward a central point

  Example: "Focus the light on this image"

• verb:   put (an image) into focus

  Example: "Please focus the image"

• verb:   become focussed or come into focus

  Example: "The light focused"

• verb:   direct one's attention on something

  Example: "Please focus on your studies and not on your hobbies"

• verb:   bring into focus or alignment; to converge or cause to converge; of ideas or emotions