Cumulative interest refers to the total interest accumulated on a principal amount over a specific period of time. There are several synonyms for this term, including compound interest, accrued interest, and interest on interest. Compound interest refers to the interest earned not only on the principal amount but also on the accumulated interest. Accrued interest is the interest that has been earned but not yet paid to the investor. Interest on interest is similar to compound interest and refers to the interest earned on the previously earned interest. These terms are all used in the financial industry and help investors understand how their money is growing over time.