Specific type of open-ended mutual fund . Invests in highly liquid short-term financial instruments with maturities typically 90 days to less than one year. Pays money market account (MMA) interest rates. Negotiable certificates of deposit (CDs), commercial paper , and treasury bills are short-term vehicles. MMFs market value remains constant at $1 per share, which differs from other mutual funds. Fluctuation occurs in the interest rate paid by them. They are not protected under the deposit insurance schemes, but, they often offer check writing privileges. Also known as money market mutual fund.