What is the difference between Chautha and Terahvin?

Chautha is the community gathering on the fourth day after death — a moment of collective mourning where the community witnesses and acknowledges the loss together. Terahvin is the gathering on the thirteenth day that marks the end of the formal mourning period and the family’s return to ordinary social life. Between these two events, the most important scriptural ceremonies occur: the Vrishotsarga on Day 11 (which prevents the soul from remaining as a wandering Preta) and the Sapindikarana on Day 12 (which elevates the soul from Preta to Pitri, or honoured ancestor). Terahvin as observed today is primarily a community feast and conclusion ceremony drawn from regional custom (Deshachar); the real scriptural work of the mourning cycle was completed on Days 11 and 12.