Notional
Also referred to as principal or face value. For fixed income instruments, including bonds and swaps, the notional is used to calculate coupon payments.
If a bond has a notional of $1,000 and a 6% coupon that is paid semi-annually, then the bond will pay $30 every 6 months ($60 per year),
$1,000 x 6% x (1/2) = $30
Notional is not the same thing as price or market value. A bond with a notional of $1,000 might be worth more or less than $1,000.