Dictionary.net

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

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 fixed reference point on the concave side of a conic section

put (an image) into focus; "Please focus the image; we cannot enjoy the movie"

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

put into focus; as of an image on a screen; "Please focus the image; we cannot enjoy the movie"

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 fixed reference point on the concave side of a conic section

A point in which the rays of light meet, after being reflected or refrcted, and at which the image is formed; as, the focus of a lens or mirror.

A point so related to a conic section and certain straight line called the directrix that the ratio of the distace between any point of the curve and the focus to the distance of the same point from the directrix is constant.

A central point; a point of concentration.

To bring to a focus; to focalize; as, to focus a camera.

A point in which the rays of light meet, after being reflected or refrcted, and at which the image is formed; as, the focus of a lens or mirror.

A point so related to a conic section and certain straight line called the directrix that the ratio of the distace between any point of the curve and the focus to the distance of the same point from the directrix is constant.

A central point; a point of concentration.

To bring to a focus; to focalize; as, to focus a camera.

The point where a system of rays of light or heat meet after being reflected or refracted; any central point.

Focused.

Focusing.

Common centre of rays which have been refracted or reflected. Central seat of a disease.

(optics) A point in which the rays of light meet after reflection or refraction, and cause great heat; any central point; -pl. FOCUSES and FOCI.

To bring to a focus; pp. focussed.

Point where rays meet; central point.

To adjust or bring to a focus; concentrate.

A point of meeting of rays of light; any point of concentration.

Geom. One of two points, as in an ellipse, the sum or difference of whose distances to any point of the curve is always the same.

The point of convergence of light-rays or of sound-waves.

Chief center of a morbid process.

A central point, or point of departure; a nucleus; a point at which a process is manifested in great intensity.

To adjust a lens or a mirror in such a way that the image is most distinctly seen.

PI. foci. The point at which rays are collected or converged by a lens or mirror. When used without qualification, the principal f. is always meant.

n. [Latin] A point in which the rays of light meet after being reflected or refracted;—a point on the principal axis of a conic section, such that the double ordinate to the axis through the point shall be equal to the parameter of the curve;—a central point; a point of concentration.

The point where the rays are collected by a burning glass; the point in the axis of a lens, where the rays meet and cross each other; a certain point in the axis of a curve.