An investment fund that holds the objective to earn interest for shareholders while maintaining a net value asset  of $1 per share. Mutual funds, brokerage firms and banks offer these funds. Portfolios are comprised of short-term (less than one year) securities representing high-quality, liquid debt and monetary instruments.

A money market fund's purpose is to provide investors with a safe place to invest easily accessible cash-equivalent assets characterized as a low-risk, low-return investments. Because of their relatively low returns, investors, such as those participating in employer-sponsored retirement plans, should not use money market funds as a long-term investment option.