1. pay back: to give someone back
money that you have borrowed from them
例：
pay somebody back
I'll pay you back tomorrow. （我明天还你钱。）
pay back something
How are you going to pay back all that
money? （这些钱你打算怎么还？）
He's paid back about half of what he owes
us. （他欠我们的钱已经还了差不多一半了。）
pay back a loan/debt etc.
After graduation, the student must begin to
pay back the loan. （学生毕业后就得开始偿还助学贷款了。）
2. repay: to pay a large amount of
money that you owe, especially to a bank
例：
The loan has to be repaid within two years.
（贷款要在两年内还清。）
There were doubts about the country's
ability to repay the debt. （大家都不确定这个国家是否真能还上钱。）
My parents lent me the money to buy a car,
and I repaid them over the next year. （我父母先借我买车的钱，我明年还他们。）
3. pay off: to finish paying back an
amount of money that you have borrowed
例：
pay off a debt/loan/mortgage etc.
The mortgage will be paid off over
twenty-five years. （贷款将在25年内还清。）
He paid off the loan six months early. （他提早半年还清了贷款。）
pay a debt/loan/mortgage etc. off
The country hopes to pay all its debts off
within twenty years. （这个国家想在20年内还清外债。）
4. pay up: to pay money that you
owe, especially when you do not want to or when you are late paying it
例：
If they don't pay up we will take legal
action. （他们要是不还钱，我们会采取法律手段。）
The company paid up eventually, but only after
repeated threats and reminders. （在不断地警告威胁之后，这个公司最终还钱了。）
5. settle:
settle an account/bill/loan etc.: to pay money that you owe someone - used especially in business
contexts
例：
Please settle this account within two weeks.
（请在两周内还清欠款。）
I settled the bill and left the restaurant.
（我把欠餐厅的饭钱结清之后就走了。）
6. clear: to finally pay all the
money that you owe, after some time or with some difficulty 还清所有的欠款
例：
This check should clear my overdraft. （这张支票应该够把我透支的金额还清了。）
We're hoping that we can clear all our
debts by the end of the year. （我们希望今年之内能还清所有欠款。）
7. give somebody their money back/give somebody a refund: to give back to someone the money that they paid for something,
especially because they are not satisfied with what they bought or there is
something wrong with it
例：
It's the wrong size. Do you think they'll
give me my money back? （尺码不对，你说他们会退钱给我吗？）
We'll give you a refund if you're not
entirely satisfied. （如果你不是非常满意，我们可以退钱给你。）
8. rebate: an amount of money that
is paid back to you, especially because you have paid too much in taxes, rent
etc. 退税
In American English a tax rebate is called
a ''tax refund''. （英式英语中，常用''tax rebate''；美式英语中，常用''tax refund''。）
例：
The Ford Citibank credit card offers a 5
percent rebate on the purchase of a new Ford car or truck. （如果用花旗银行福特信用卡买全新的福特轿车或卡车，都将取得5%的退税。）
tax/rent rebate
We were delighted to hear that we were
entitled to a tax rebate of over £1000. （得知我们将有£1000多的退税，我们很高兴。）