Snapping a six-session winning streak, the Sensex at the Bombay Stock Exchange dropped 83 points, or 0.4 percent, to 18,763, today, on profit-booking by investors. The Nifty at the National Stock Exchange fell 20 points, or 0.4 percent, to 5,627. Stock markets in Japan, South Korea, and Singapore rose between 0.5 percent and 1.2 percent.