Definition:

Interest rate is the amount charged, expressed as a percentage of principal, by a lender to a borrower for the use of assets. Interest rates are typically noted on an annual basis, known as the annual percentage rate (APR). The assets borrowed could include, cash, consumer goods, large assets, such as a vehicle or building. Interest is essentially a rental, or leasing charge to the borrower, for the asset’s use. In the case of a large asset, like a vehicle or building, the interest rate is sometimes known as the “lease rate”. When the borrower is a low-risk party, they will usually be charged a low interest rate; if the borrower is considered high risk, the interest rate that they are charged will be higher.1

Example:

A low-risk borrower received a 4% interest rate on their auto loan.

1 Source: Investopedia