An unusual home mortgage arrangement in which the borrower makes payments every two weeks instead of once a month. In a biweekly mortgage you make 26 annual payments of half your monthly mortgage amount, thanks to the number of weeks in a year. So under this arrangement you'd make the equivalent of 13 monthly payments each year instead of 12. The good news is the extra payment reduces the principal that you owe -- thus allowing you to pay off a 30-year mortgage in much less time. Then again, you can normally achieve the same effect by simply adding to the amount that you pay on your monthly mortgage.