学员问：pay for/pay back/pay off 钱到底怎么付？

Tyger答

for目的，pay付钱，pay for为……买单，

back回，pay back把钱付回来，偿还

off分离，pay off偿还后和债务分离

I paid for a LV with my credit card，I paid the loan back little by little，I finally paid off my debt a year later. 

总评：需要从for，back，off的本质突破，消灭固定搭配。