The observance of Ekadashi is the Hindu practice of fasting and heightened devotion on the eleventh day of each half of the lunar month, the eleventh day after the new moon and after the full moon, making it a fortnightly discipline that falls roughly twice a month throughout the year. The day is sacred above all to Vishnu, and its observance is especially central to the Vaishnava devotional traditions, for whom keeping Ekadashi is among the most important of regular religious duties. The tradition holds the fast to purify body and mind, to burn away accumulated sin, and to advance the devotee toward liberation, and a rich body of story literature attaches particular merits and origins to the many named Ekadashis of the year.
The fast takes various forms according to the strictness of the observer: some abstain from all food and even water for the full day, others take only fruit, milk or water, and a widespread rule forbids grains and pulses on Ekadashi, so that even those who do not fast completely alter their diet. The day is given to increased worship, the repetition of Vishnu's names, the reading of scripture and the keeping of vigil. Some Ekadashis are held to be especially potent, among them the Vaikuntha Ekadashi, on which the gate of Vishnu's heaven is said to open to the faithful, and are observed by great numbers with particular devotion.