是on vacation还是on a vacation 它们有什么区别?

是go on vacation 还是go on a vacation?是go for vacation还是go for a vacation? go on vacation还是go on a vacation? 是on vacation还是on a vacation 它们有什么区别? 是in vacation,还是on vacation,还是atvacation? a vacation 前用on还是for 请问是in summer vacation还是on summer vacation? 是travel to vacation,还是travel on vacation vacation可数么是go on vacatin 还是go on a vacatino on a vacation是什么意思 on a vacation造句 应该用in vacation还是on vacation go for one's vacation /on vacation/ take a vacation vacation 前用什么介词?是in?还是on? go on vacation 和go on a vacation 的区别? go on a vacation与go on vacation的区别go on a vacation与go on vacation一样吗? for vacation on vacation take a vacation on holiday for vacation 的区别 到底是on their vacation 还是 for their vacation啊?求解! go on vacation 和go on a vacation 有什么区别这两个是一样的吗?