from
The Collaborative International Dictionary of English v.0.48
dollar bill \dollar bill\
A paper note printed by the Treasury, or by one of the
Federal Reserve Banks under authority of the treasury, having
the value of one dollar. Also five dollar bill, ten dollar
bill, etc.: notes with the value of five, ten, etc. dollars.
Prior to 1964 such notes could be redeemed for the equivalent
dollar value in silver coins, but in that year the backing of
the currency with silver was discontinued. Such notes not
convertible into precious metals at a fixed rate are called
"fiat money", receiving their value solely from the good
faith of the issuing government and the confidence of those
using the currency.
[PJC]