Sandhi is a junction, and the word covers several in Jyotish. Bhava sandhi is the meeting of two houses, where a graha is read as weak and its results as uncertain, since it belongs to neither. Rasi sandhi is the meeting of two signs, and the junction of a water sign with a fire sign is the gandanta, the hardest of them. Sandhya is the twilight - BPHS defines it as three ghatikas, about seventy-two minutes, before sunrise and after sunset - and a birth in it is one of the classical evils to longevity.