MUM is a sacred Sanskrit mantric syllable, here written in Tibetan.

It is the seed syllable of Praja-Paramita, the mother of all Buddhas. She personifies the Buddha's teachings on the meaning of emptiness compassion and the paths leading to a mind freed from habits that create suffering.

Prajna-Paramita is called "the Mother" because she is the matrix that gives birth to all the realization of all the Buddhas.

The Prajna-Paramita sutras are a collection of wrttings that contain the famous Heart sutra. Here are the essential lines:

Form is emptiness
Emptiness is form.
Emptiness is not other than form.
Form is not other than emptiness


This syllable iis used in meditation practices that involve vizualizations.

Prajna-Paramita as a practice:

Machig Labdron(11th century female), is one of the main proponants of using Prajna-Paramita in meditation practice as a yidam or deity. Machig recieved the teachings while in retreat at age 41. During the retreat Tara appeared to her and among other things told her that she was the mind emmanation of the great Yum Chenmo, or Prajna-Paramita, the nature of all phenomena, emptiness, the essence of reality. She then gave her the visualizations for a meditation using Prajna-Paramita as the yidam or main deity of the practice. The story begins with Tara's aspirations and prayers out of which arises a golden/orange bindu or sphere, ablaze with light and marked with the syllable MUM. This then transforms into Yum Chenmo or the great mother Prajna-Paramita herself.