Русско-англо-русский юридический словарь

The loan principal refers to the amount of money you borrow from a lender, whereas interest refers to the charge you pay to borrow that money. (Deskera)

Unlike normal Interest on Debt, PIK Interest (PIK = “Paid-in-Kind”) accrues to the loan principal rather than being paid in cash, which results in an increasing loan balance and higher interest payments in the future. (Breaking Into Wall Street)