The Sensex at the Bombay Stock Exchange on Monday lost 333 points, or 1.8 percent, to close below the 18,000-mark, at 17,993 on weak global markets, amid a deepening euro-zone debt crisis. The Nifty at the National Stock Exchange slipped 100 points, or 1.8 percent, to 5,387.Stock markets in Japan, China, Hong Kong, Singapore and South Korea lost between 1.5% and 2.9%.