obsolescence

n.过时；作废

obsequious, obsequiously, obsequiousness, observable, observance, observant, observantly, observation, observation car, observation post, observatory, observe, observer, observing, obsess, obsessed, obsession, obsessional, obsessive, obsessively, obsolescent, obsolete, obssess, obstacle, obstacle race, obstetric, obstetrician, obstetrics, obstinacy, obstinate, obstinately, obstreperous, obstreperously, obstreperousness, obstruct, obstruction, obstructionism, obstructionist, obstructive, obstructively,