Both mortgage and security interest relate to securing the repayment of a loan by providing a collateral.
Mortgage is a legal instrument, whereby real property is granted as a security for the repayment of a loan. In case of a payment default, the mortgagee may acquire the title to the property which has been used to secure the loan. The person who holds a mortgage, that is the right to eventually acquire titel to the property is the credit is not repaid.
Security, on the other hand, is a term used more frequently in commercial transactions, where the the property in question is usually not real property but products or goods used in the stream of commerce. Security interest are governed in various jurisdictions by the law of secured transactions as opposed to the law regulating property issues.
In summary, mortgage is strictly linked, and restricted, to real property used as collateral, while security is a term used in commmercial transactions.
