Fund that concentrates primarily on short-term government securities, certificates of deposit with maturities less than one year, and high-quality interest-bearing corporate debt. The fund is a pool of money from many investors from which interest is paid to these investors on the income earned by that pool of money. Income and yield fluctuate on a daily basis, but each share in the mutual fund maintains a constant value of $1, resulting in no capital gains or losses. These funds are ideal for short-term needs. Since these funds invest in financial instruments whose maturities are very short, reinvesting is on a continuous basis. Thus, as interest rates rise or fall, the funds' yields will correspond accordingly.