The account carries interest of 4%.

該存款有4%的利息。

The interest is added to your account every year.

每年的利息都加到你的存款中。

The interest rate for the savings account is 4%.

儲蓄存款的利率是4%。

It varies from time to time. At present it is 6%.

（年息）每個時期都不同，現在是六厘。

Useful Words and Phrases

interest rate 利率

simple interest 單利

compound interest 復利

legal interest 法定利息

prime rate 優待利率

payable interest 應付利息

lending rate 貸款利率

usury 高利貸

the subsidy rate for value-preserved savings 保值儲蓄補貼率