A mutual fund that invests predominately or exclusively in securities representing a single thing. For example, a theme fund may invest only in energy stocks, securities related to real estate, or in investment vehicles that conform to a set of ethical standards. While some theme funds can be relatively diversified, many are exposed to the risk that a downturn in the "themed" industry will impact the fund disproportionately. See also: Green fund, Islamic fund, Ethical fund.
An investment company that chooses investments according to a particular issue or theme. For example, a fund built on an agricultural theme might invest in the equities of farm equipment manufacturers, chemical companies, and other firms that sell agricultural products. Likewise, an investment company might choose to invest in equities that would reflect an ecological or baby-boomer theme.