in holiday 泛指放假,但说话人说话的时候并不在放假. 如,i'd like to stay with my families in holiday. in the holiday 指特定的假期,根据上文的延续. 如,Christmas is a spcial holiday in western countries.In the holiday,people usually stay with their families. on holiday 处于放假的状态 如,i'm on holiday now.类似有on duty 上班中
