A vigil is a period of purposeful sleeplessness or observance, and a prayer vigil involves praying while holding a vigil. The word "vigil" comes from the Latin word "vigilia," meaning "wakefulness."
Vigils are commonly held before a feast day or after a death. They are typically held at night by an assembly of many people. One common variation is the candlelight vigil. During a candlelight vigil, attendees hold candles in remembrance of people who died in a disaster, massacre or other tragedy. Most likely, the best-known vigil related to a feast day is the Easter Vigil, which is held on Holy Saturday, the night before Easter.