off and on

断断续续，不时地

odourless, odyssey, OECD, oecumenical, Oedipus complex, oesophagus (also esp US esophagus), oestrogen, of, of all time, of course, of importance, of itself, of late years, of necessity, of one's own, of the moment, of...importance, of...interest, of...value, off, off balance, off chance, off duty, off of, off(-), off-beat, off-cut, off-day, off-duty, off-grade, off-handedly, off-key, off-licence, off-line, off-load, off-peak, off-putting, off-season, off-stage, off-street,