Here is the simple, traditional difference during Paryushan:

• Chauvihār pachkhan

- Vow from sunset until next sunrise. - No eating and no drinking at all (not even water). - Purpose: night-time ahimsā (to avoid harming tiny beings) and building saiyam (discipline). - Reference:

• Tivihār (Tivihar) pachkhan

- Stricter vow from sunset until next sunrise. - No eating, no drinking, and no medicine (āushadhi), except genuine health emergency as guided by your Guru. - Often observed more strictly during fasts (e.g., Tivihar upvās = no food or water the whole day, and after sunset still nothing). - Reference:

Notes on traditions

• Shvetāmbār and Digambar both uphold “no night-eating.” Wording and small allowances (like medicine in illness) are taken as per one’s Guru and local maryādā.
• Always take pachkhan formally (before a monk/nun or at home with right intent) and keep it until sunrise.

Essence: Both stop night intake; Tivihār adds the restraint of medicine, so it is one step stricter than Chauvihār.