What do yo mean by the lot size F&O of NSE?

The minimum number of shares required to enter an Options contract is called a lot size. The NSE F&O (Futures & Options) lot size varies from stock to stock and index to index. Nifty 50 has a lot size of 75, while Bank Nifty has a lot size of 40. Reliance Industries has a lot size of 1000 while TCS has 250. BSE and NSE decide the lot size. These exchanges may revise the lot sizes of stocks and indexes as needed.