n (uncountable|photography|cinematography) The fact of the convergence of light on the photographic medium.
n (uncountable|photography|cinematography) The quality of the convergence of light on the photographic medium.
n (computing|graphical user interface) The indicator of the currently active element in a user interface.
n (linguistics) The most important word or phrase in a sentence or passage, or the one that imparts information
v (transitive) To adjust (a lens, an optical instrument) in order to position an image with respect to the focal plane.