A bij-mantra is a seedling of a mantra. It is this seedling that shoots of the science of Mantra spread. The energy of any mantra lies in its beeja. The chanting of a mantra is efficacious only if an appropriate bij is selected. The bij activates the deity of the mantra.
Each bij-mantra contains groups of letters. Example of bīj-mantra include Om, Aim, Kreem and Kleem.