Stock Market Today: The Sensex and Nifty opened marginally lower on June 20. The Sensex opened flat with a negative bias at 81354.85 down by 0.008 per cent or 7.02 points lower. Likewise, the Nifty 50 started with some marginal losses as it opened 5.6 points lower or 0.022 per cent lower at 24787.65.