observatory

n.天文台，气象台，了望台

oboe, oboist, obscene, obscenely, obscenity, obscur, obscure, obscurely, obscurity, obsequies, obsequious, obsequiously, obsequiousness, observable, observance, observant, observantly, observation, observation car, observation post, observe, observer, observing, obsess, obsessed, obsession, obsessional, obsessive, obsessively, obsolescence, obsolescent, obsolete, obssess, obstacle, obstacle race, obstetric, obstetrician, obstetrics, obstinacy, obstinate,