focus

v.(使)聚焦，(使)集中 n.焦点

flying picket, flying squad, flying start, flying tackle, flying visit, flyleaf, flyover, flysheet, flyweight, flywheel, FM, FO, foal, foam, foamy, fob, focal, focal length (also focal distance), focal point, focsle, focus on, focus...on, fodder, foe, foetal (US fetal), foetus (US fetus), fog, fog-bank, fog-bound, fog-horn, fog-lamp, foggy, fogy (also fogey), foible, foil, foist, fold, foldaway, folder, folding,