Definition from Wiktionary, the free dictionary
उपनयन • (upanayana) n
- the act of leading to or near, bringing.
- employment, application.
- introduction (into any science).
- leading or drawing towards one's self.
- that ceremony in which a Guru draws a boy towards himself and initiates him into one of the three twice-born classes (one of the twelve संस्कारs or purificatory rites [prescribed in the धर्म- सूत्रs and explained in the गृह्य- सूत्रs] in which the boy is invested with the sacred thread [different for the three castes] and thus endowed with second or spiritual birth and qualified to learn the वेद by heart ; a Brahman is initiated in the eighth year [or seventh according to हिरण्यकेशिन् ; or eighth from conception, according to शाङ्खायन etc.], a क्षत्रिय in the eleventh, a वैश्य in the twelfth ; but the term could be delayed)