A vigil (from the Latin vigilia, meaning wakefulness) is a period of purposeful sleeplessness, an occasion for devotional watching, or an observance.
It can also be the eve of a religious festival observed by staying awake as a devotional exercise or ritual devotions observed on the eve of a holy day , such as the Easter Vigil held on Holy Saturday. In the Eastern Orthodox Church an All-Night Vigil is held on the eves of Sundays and all major feasts during the liturgical year.
In Christianity, especially the Eastern Orthodox and Roman Catholic traditions, a vigil is often held when someone is gravely ill or dying. Prayers are said and votives are often made. Vigils extend from eventual death to burial, ritualistically to pray for a loved one, but more practically so they are never alone.
During the Middle Ages, a squire on the night before his knighting ceremony was expected to take a cleansing bath, fast, make confession, and then hold an all-night vigil of prayer to God in the chapel, readying himself for his life as a knight. He would dress in white, which was the symbol for purity.