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English definition of “focus”

focus

noun [C] (SCIENCE)    /ˈfəʊ.kəs/ US  /ˈfoʊ-/ (plural focuses or formal foci)
(in physics) the point where waves of light or sound that are moving towards each other meet: the focus of a lensOptics, microscopy and lasersEyesight, glasses and lenses be in/out of focus describes a photograph that is clear/not clearPhotography
(Definition of focus noun (SCIENCE) from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
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