The right of shareholders to use dividends to buy more shares of a publicly-traded company or mutual fund. Many publicly-traded companies and most mutual funds carry a reinvestment privilege as a perk for investors. Shareholders who avail themselves of the reinvestment privilege do not pay any additional fees on the extra shares they buy.
The prerogative of a mutual fund shareholder to have dividends used to purchase additional shares in the fund. Most mutual funds give their shareholders reinvestment privileges and most do not charge fees for the purchase of the new shares.