Русско-англо-русский юридический словарь

Debt principal is the amount owed to the government by a borrower or other debtor, excluding interest, penalties, administrative costs, loan fees, and prepaid charges. (U.S. Department of the Treasury (.gov))

Mandatory Amortization: The required repayment of some amount of the original debt principal, typically meant to de-risk the lender's investment over time. (Wall Street Prep)

First, some of your student loans, especially ones subsidized by the government, carry low interest rates. As a result, you are not significantly adding to the debt principal by paying it off over the term of the loan. (CNN Money)

Although 50 years might under some circumstances be considered as a long time for the principal of a debt to be outstanding, we must take into consideration the substantial nature of the [petitioner’s] business . . . (The Tax Adviser, a monthly publication of the American Institute of CPAs)