The parent mentioned Compound Interest. Many people, including non-native speakers, may be unfamiliar with this word. Here is the definition^{(In beta, be kind):}

The addition of interest to the principal sum of a loan or deposit is called compounding. Compound interest is interest on interest. It is the result of reinvesting interest, rather than paying it out, so that interest in the next period is then earned on the principal sum plus previously-accumulated interest. Compound interest is standard in finance and economics. [View More]

^{See also: Curator | Web Crawler | Nominal Interest Rate | Interest For Money | Interest Upon Interest}

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