maximum clarity or distinctness of an image rendered by an optical system
"in focus"
"out of focus"
maximum clarity or distinctness of an idea
"the controversy brought clearly into focus an important difference of opinion"
a central point or locus of an infection in an organism
"the focus of infection"
a point of convergence of light (or other radiation) or a point from which it diverges
"The photographer adjusted the lens until the distant streetlamp appeared as a sharp, bright dot rather than a blurry glow."
a fixed reference point on the concave side of a conic section
"The optical engineer adjusted the lens until its focus aligned perfectly with the focal point of the parabolic mirror's concave side."
A point at which reflected or refracted rays of light converge.
"The photographer adjusted the lens until the distant streetlights appeared as sharp points where their reflected rays converged in focus."
In plain English: Focus is the specific point where your attention is directed.
"The main focus of the meeting was on improving customer service."
Usage: In everyday conversation, focus refers to the state of concentrating attention or effort on a specific task, person, or subject. Use this noun when describing mental engagement rather than the technical optical point where light rays meet.
To concentrate during a task.
"She had to focus on her breathing before taking the final shot in the competition."
In plain English: To focus means to direct your attention or effort toward something specific.
"She needs to focus on her homework before dinner."
Usage: Use focus to mean directing your mental attention or effort toward a specific task or goal. It is often followed by on when indicating what is being concentrated upon.
The word comes from Latin focus, meaning "hearth" or "fireplace," which traveled into English to describe a central point of heat or light. Astronomer Johannes Kepler later applied this term to mathematics and science, using it to describe the specific points in an elliptical orbit where light rays would converge if reflected off the shape's surface.