Written instrument creating a lien on real property, or by which title to the real property is held as security for the repayment of a debt. The owner (the mortgagor) borrows money from a lender (the mortgagee), and the loan is documented with a promissory note and secured by a mortgage or other security interest. If the borrower does not repay the obligation, the lender can get title to the real property or sell the property at auction and reimburse itself for the loan proceeds, interest, and expenses.