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 另外补充一下,如果你前面曾经提起过某个节日,而现在针对这个节日说on,就要用on the holiday,特指在这个节日。否则,用on holiday.