n (countable, optics) A point at which reflected or refracted rays of light converge.
n (countable, geometry) A point of a conic at which rays reflected from a curve or surface converge.
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 (uncountable) Concentration of attention.
n (countable) Something to which activity, attention or interest is primarily directed.
n (countable, seismology) The exact point of where an earthquake occurs, in three dimensions (underneath the epicentre).
n (graphical user interface) The status of being the currently active element in a user interface, often indicated by a visual highlight.
n (linguistics) The most important word or phrase in a sentence or passage, or the one that imparts information.
n An object used in casting a magic spell.
v (transitive) To cause (rays of light, etc) to converge at a single point.
v (transitive, optics) To adjust (a lens, an optical instrument) in order to position an image with respect to the focal plane.
v (intransitive, optics, of a lens, optical instrument, etc.) To adjust itself or be adjusted such that light from a scene converges appropriately to create a clear image.
v (transitive) To direct attention, effort, or energy to a particular audience or task.
v (intransitive) To concentrate one’s attention.
v (intransitive, followed by on or upon) To concentrate one's attention on something; to have as one's central point of interest, concern, etc.
v (computing, graphical user interface, transitive) To transfer the input focus to (a visual element), so that it receives subsequent input.
v (accounting, formerly) To aggregate figures of accounts.