GLOSSARY Terms related to the Federal Reserve, banking and economics   A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |   variable rate A variable-rate agreement, as distinguished from a fixed-rate agreement, calls for an interest rate that may fluctuate over the life of the loan. The rate is often tied to an index that reflects changes in market rates of interest. A fluctuation in the rate causes changes in either the payments or the length of the loan term. Limits are often placed on the degree to which the interest rate or the payments can vary.   vault cash Cash kept on hand in a depository institution's vault to meet day-to-day business needs, such as cashing checks for customers; can be counted as a portion of the institution's required reserves.