"ON my summer holiday I will go skiing" in X "DURING my summer holiday I will go skiing" "People often relax ON THEIR HOLIDAYS" Holidays is plural because people is plural, many to many relationship, you might have a whole family (many people) going on a single holiday together (one) in which case you'd use holiday and not holidays. "My neighbours often relax ON THEIR HOLIDAY together" or you might have a single person (one) that goes on a lot of holidays (many) "My neighbour told me that he loves to water ski when he is ON HIS HOLIDAYS" in X "People often relax DURING THEIR HOLIDAYS" "This year I HAVE 30 days of holiday from my job" "This year I HAVE a holiday in the summer" have == possess "This year I will TAKE a holiday in Italy" "I think I will TAKE a holiday to China" take == to go on "I GO ON HOLIDAY to China" "I usually GO ON MY HOLIDAYS to China" go on == to vacation There is no hard and fast rule here, it's context dependent. Try providing some sentences that you think are correct and we can correct them.