Return to the Mortgage Glossary Home to view explanations for all mortgage terms. What follows is the definition for the term Principal as it relates to mortgages in the UK. Principal In relation to mortgages, Principal is the amount of money which you have borrowed, not including the interest which is calculated and paid on it. In the case of an interest-only mortgage, it would be the amount you would be expected to pay at the end of the mortgage term (typically 25 years). Previous 10 terms < Portable Mortgages < Negative Equity < Mortgage Protection Policy < Mortgage Offer < Mortgage Indemnity Premium < Mortgage < Local Search < Legal Fees < Leasehold < Joint Tenants Next 10 terms Redemption Penalty  > Repayment Mortgages  > Self Certification  > Self-employed  > Survey  > SVR (Standard Variable Rate)  > Valuation  > Valuation Fee  > Accident, Sickness and Unemployment Insurance (ASU)  > Added To Loan  >