Interest is the cost of using money. The interest rate paid is usually expressed in annual terms though money market instruments may have a shorter term than one year. An interest rate is determined by dividing the amount of interest paid by the principal amount borrowed. For example, if a $1000 bond pays $85 in interest for one year, the annual interest rate is 8.5 percent. In the U.S. some interest-bearing bonds, such as municipals, entitle the bearer to an exemption from certain taxes on interest income. The interest paid by a company on its outstanding debt as well as the interest paid by a homeowner on his/her mortgage, is deductible from income as an expense and so can reduce the amount of tax owed.
　　利息是使用貨幣的成本。利率的支付形式通常以年為期限，雖然金融市場票據會有一個更短的時間。利率的制定取決于借款本金所劃分的利息。舉個例子，如果1,000美元的債券每年支付85美元的利息，那么年利率就是8.5%。美國有一些有息債券，如政府債券，它允許持有人在利息收益上有一定的免稅。公司未償債務和按揭住房的屋主需支付的利息可以作為一項費用減少他們的應交稅金。