Negative Amortization
Some adjustable rate mortgages allow the interest rate to fluctuate independently of a required minimum payment. If a borrower makes the minimum payment it may not cover all of the interest that would normally be due at the current interest rate. In essence, the borrower is deferring the interest payment, which is why this is called "deferred interest." The deferred interest is added to the balance of the loan and the loan balance grows larger instead of smaller, which is called negative amortization.