1.pay,pay for
两者都可表示“付款”,但用法不同：
pay用作及物动词时,后面接表示人的词语,即pay sb.意为“付款给某人”.如：
He paid me five yuan.他付了我五元钱.
Have you paid the doctor yet?医生的酬金付了吗?
pay for中的pay为不及物动词,其宾语多为物,即pay for sth.,意为“付款买某物”；其宾语为人时,即pay for sb.,意为“替某人付款.”如：
Shall I pay for you?我替你付款好吗?
He can't pay for the TV set at the moment.他现在还不能给这台电视机付款.
How much did you pay for all these things?你买所有这些东西一共花了多少钱?
另外,表示“给某人钱买……”,可用“pay（sb.）＋钱＋for sth.”.如：
I paid the shopkeeper 10 yuan for the book.我向店主付了十元钱买这本书.
2.正因为Pay是不及物动词,所以必须接介词才能有宾语,相反,put是及物东西,所以可以说put it on