Sannyasa (संन्यास) is the fourth and final ashrama — total renunciation. The word comes from sam-ni-as, "to set down completely". The sets down possessions, social role, ritual fire, and the very identity of householder, freeing the whole of life for the single pursuit of moksha.
Entering
The classical ceremony of sannyasa-grahana is solemn. The aspirant performs a final fire ritual, mentally offers up the household fires into himself, takes the vows of non-injury (ahimsa), truth (satya), and renunciation, receives the ochre robes (kashaya) and staff (danda) from his teacher, and is given a new name. From that moment he is, by tradition, dead to his former life.
The Sannyasin's Life
A owns little: a robe or two, a bowl, a staff, perhaps a book or a rosary. He eats one simple meal a day, taken as alms. He sleeps where he can — under a tree, in a temple, in a monastery (matha). He keeps no fixed home for long. His days are given to meditation, study of the Upanishads, japa, and teaching such seekers as come to him.
Inner Renunciation
The outer marks of exist to support the inner. The robes proclaim a vow that the wearer is bound to honour. The staff symbolises the discipline of mind. The single meal limits the play of senses. None of these means anything if the inner attachments remain. The Bhagavad Gita 6.1 warns that one who has merely set aside fire and ritual without renouncing the fruits of action is no true .
The Four Kinds
Later tradition distinguishes types of by the degree and form of withdrawal — kuticaka, bahudaka, hamsa, paramahamsa — culminating in the paramahamsa, the highest form, in which all formal marks are also dropped and the renunciate moves freely beyond convention, recognised only by the depth of his realisation.
Lineages
Adi Shankara is traditionally credited with formalising the Dashanami sampradaya, the ten orders of Advaita sannyasins (Saraswati, Bharati, Puri, Tirtha, Ashrama, Giri, Parvata, Sagara, Vana, Aranya), each associated with one of the four mathas he established. Other Vedantic sampradayas — Sri Vaishnava, Madhva, Gaudiya — have their own renunciate orders.
Outside the Stage
Not everyone reaches through the orderly progression of the four stages. The texts also allow vidvat-sannyasa, renunciation born of mature knowledge, undertaken whenever the inner readiness arises. Shankara himself took as a youth. The decisive thing is the inner ripeness, not the age.
A Witness for All Stages
The sannyasin's life witnesses to something the other ashramas also need to remember: that finally nothing held belongs to us, that the self is more than its roles, and that the deepest freedom lies in letting go. Even those who never take formal are quietly oriented by its example.