Upanayana is the initiation

Initiation

Initiation is a rite of passage ceremony marking entrance or acceptance into a group or society. It could also be a formal admission to adulthood in a community or one of its formal components...

 ritual

Ritual

A ritual is a set of actions, performed mainly for their symbolic value. It may be prescribed by a religion or by the traditions of a community. The term usually excludes actions which are arbitrarily chosen by the performers....

 by which initiates are invested with a sacred thread, to symbolize the transference of spiritual knowledge .
In Hinduism

Hinduism

Hinduism is the predominant and indigenous religious tradition of the Indian Subcontinent. Hinduism is known to its followers as , amongst many other expressions...

 and Buddhism

Buddhism

Buddhism is a religion and philosophy encompassing a variety of traditions, beliefs and practices, largely based on teachings attributed to Siddhartha Gautama, commonly known as the Buddha . The Buddha lived and taught in the northeastern Indian subcontinent some time between the 6th and 4th...

, a Sacred Thread (Sanskrit

Sanskrit

Sanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...

: यज्ञोपवीतम्, yajñopavītam) is a thin consecrated

Consecration

Consecration is the solemn dedication to a special purpose or service, usually religious. The word "consecration" literally means "to associate with the sacred". Persons, places, or things can be consecrated, and the term is used in various ways by different groups...

 cord, composed of distinct cotton strands, worn to symbolize coming of age. The sacred thread is known by many names (varying by region and community), such as Janeu, Lagun, Yajnopavita, Yagyopavit, Yonya and Zunnar.

The sacred thread ceremony (Sanskrit: उपनयनम्, upanayanam) that invests the wearer with the sacred thread is often considered a socially and spiritually significant rite (or samskara

Samskara

Samskara may refer to:* Saṃskāra, Hindu rites* Saṃskāra , in Buddhism, mental and volitional formations* Samskara , a technique in ayurvedic medicine...

).