(followed by on or upon) To concentrate one's attention.

“I have to focus on my work.”

To cause (rays of light, etc) to converge at a single point.

To adjust (a lens, an optical instrument) in order to position an image with respect to the focal plane.

“You'll need to focus the microscope carefully in order to capture the full detail of this surface.”

The action of the verb to focus.

Used for or pertaining to focusing.