The length of time a lender is willing to offer a borrower the quoted interest rate. Rate commitments can vary from 30 to 180 days.

The number of days the lender will guarantee the mortgage rate on a mortgage approval. This can vary from lender to lender anywhere from 30 to 120 days.

A written promise by a lender to lend money to a borrower at a stated rate of interest -- usually time limited.

This term is used in reference to the lock-in rate as well as the agreements on any caps and margins for adjustable rate loans.