often

ad.经常，常常

officer, official, officialdom, officialese, officially, officiate, officious, officiously, officiousness, offing, offish, offline, offprint, offset, offshoot, offshore, offside, offspring, oft, oft-times, ogle, ogre, ogrish, oh, Ohio, ohm, OHMS, oho, oil, oil rig, oil slick, oil well, oil-bearing, oil-colour (also `oil-paint), oil-fired, oil-painting, oil-palm, oil-tanker, oilcake, oilcan,