In Jainism, chauvihaar upvaas is a specific form of fasting (upvaas). The term "chauvihaar" comes from two words: "chovi" meaning "four" and "vihar" meaning "to abstain." Thus, chauvihaar refers to abstaining from all four types of intake: food and water both during the day and at night.

In chauvihaar upvaas, a Jain practitioner refrains from consuming any food or water from sunset of the previous day until sunrise of the following day (typically a period exceeding 36 hours). This is considered a more rigorous fast compared to other types, such as "beasu upvaas" (where only food is avoided but water is allowed).

Key points about Chauvihaar Upvaas:

• No food or water is consumed after sunset until after sunrise the day after the fast.
• It is practiced as a means of penance, self-control, and spiritual purification.
• It is commonly undertaken during important Jain festivals such as Paryushan and Ayambil Oli.

Purpose in Jainism: Chauvihaar Upvaas is believed to help in reducing karma, controlling desires, and fostering spiritual growth by practicing self-restraint (samyam) and non-attachment (aparigraha).

Note: As with all Jain fasting practices, individuals are encouraged to consider their health and consult with spiritual guides or family elders before undertaking strict fasts.