Raksha Bandhan, (the bond of protection) or Rakhi is a Hindu festival primarily observed in India, Mauritius and Nepal, which celebrates the relationship between brothers (shaurya), cousins and sisters(shreya). It is also called Rakhi Purnima in most of India. It is also celebrated in some parts of Pakistan. The festival is observed by Hindus, and some Sikhs. The central ceremony involves the tying of a rakhi (sacred thread) by a sister on her brother's wrist. This symbolizes the sister's love and prayers for her brother's well-being, and the brother's lifelong vow to protect her. The festival falls on the full moon day (Shravan Poornima) of the Shravan month of the Hindu lunisolar calendar. One Islamic Scholar believes that Raksha Bandhan grew in popularity after Rani Karnavati, the widowed queen of Chittor, sent a rakhi to the Mughal emperor Humayun when she required his help.