What is "upanayana"

n. An initiation ceremony undergone by Hindu boys over the age of seven belonging to the highest three castes, marking the start of their formal education.

Upanayana is one of the traditional saṃskāras (rites of passage) that marked the acceptance of a student by a guru (teacher) and an individual's entrance to a school in Hinduism. The tradition is widely discussed in ancient Sanskrit texts of India and varies regionally. The sacred thread (yajnopavita) is received by the boy during this ceremony, that he continues wearing across his chest thereafter.

The upanayana was restricted in many medieval Indian texts to the upper three of the four varnas (castes) of society — brahmins, kshatriyas and vaishyas. However, Vedic period texts such as the Baudhāyana Grihyasutra encouraged all members of society to undergo the upanayana, even shudras. Women were encouraged to undergo upanayana in ancient India before they started Vedic studies or before their wedding.