Akhara or akhada is a Sanskrit word denoting a place of practice with facilities for board, lodging and education for a particular sect or order. It can either refer to a training hall used by martial artists or a monastery for religious renunciates.
In its earliest usage, the term akhara referred to training halls for professional fighters. Ghurye goes so far as to translate akhara to mean “military regiment”. When the 8th-century philosopher Adi Shankaracharya founded the first religious akhara, he divided the ascetics into two categories: astradhari or weapon-holders and shastradhari or scripture-holders. The former refers to the Naga sadhu akhara, a highly militant order created by Shankacharya to act as a Hindu army. Although they still carry weapons, the modern Naga rarely practice martial arts aside from wrestling. The akhara used by wrestlers still have dirt floors to which water, red ochre, buttermilk and oil are added. As with sadhu, South Asian wrestlers are expected to live a pure life, refraining from sex and owning few material possessions. The Nihang and other Sikhs also sometimes use akhara as their training grounds.
The seven akhara founded by Shankacharya were Mahanirvani, Niranjani, Atal, Avahan, Agni and Ananda Akhara. Today there are three major akhara (Juna, Mahanirvani and Niranjani) and three minor akhara (Atal affiliated with Mahanirvani, Ananda affiliated with Niranjani, and Avahan affiliated with Juna). The small Brahmachari akhara named Agni is also affiliated with Juna. Smaller akhara may be set up as an affiliate to a larger group or occasionally due to disagreements over succession. The akhara with the most sadhu is Juna, followed by Niranjani and Mahanirvani.
Akhara are classified into different Sampradaya based on their traditional systems. Shaiva for followers of Shiva, Vairagi for followers of Vishnu, Kalpwasis for followers of Brahma, Udasin for followers of Sikhism, etc. 
An akhara is divided into 8 dava (divisions) and 52 marhi (centres). Each marhi is governed by a mahant. The top administrative body of the akhara is Sri Pancha (the body of five), representing Brahma, Vishnu, Shiva, Shakti and Ganesha. It is elected on every Kumbha Mela and the body holds its post for 4 years. The head of the akhara is the Acharya Mahamandaleshwara, followed by other Mahamandaleshwara, Mandaleshwara and Sri Mahant. (All can be considered Gurudeva in their own right).
- Akhil Bharatiya Akhara Parishad (All India Akhara Council)
- Nirmohi Akhara
- Shri Dattatreya Akhara
- Guru Hanuman Akhara
- The Sikh Encyclopedia NIRMAL PANCHAITI AKHARA
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