# Economic Definition of compound interest. Defined.

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**Term compound interest Definition**: Interest that's added to a principal at regular intervals such that each subsequent interest calculation is based on the original principal and the added interest. For example, suppose you have a $100 savings account that pays 5 percent interest. Without compound interest, such that your 5 percent interest is paid only at the end of a year, you will have exactly $105 in one year. However, if your interest is compounded each month you end up with $105.12 after a year. The extra 12 cents comes from interest on the interest paid the first month, interest on the interest paid the second month, interest on the interest paid the third month... well I could go on.

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