interest rate

rate of the money that is paid for a financial service (loan, etc.)

For other senses of this word, see interest (disambiguation). Interest is a fee paid on borrowed assets. By far the most common form these assets are lent in is money, but other assets may be lent to the borrower, such as shares, consumer goods through hire purchase, major assets such as aircraft, and even entire factories in finance lease arrangements. In each case the interest is calculated upon the value of the assets in the same manner as upon money.
See more at Wikipedia.org...

Noun
1. the percentage of a sum of money charged for its use
(synonym) rate of interest
(hypernym) rate, charge per unit
(hyponym) discount rate, discount, bank discount

The monthly effective interest rate. For example, the periodic rate on a credit card with an 18% annual percentage rate is 1.5% per month.