The NSE's key index is the S&P CNX Nifty, known as the NSE NIFTY (National Stock Exchange Fifty), an index of fifty major stocks weighted by market capitalization. Nifty Fifty was an informal term used to refer to 50 popular large cap stocks on the New York Stock Exchange in the 1960s and 1970s that were widely regarded as solid buy and hold growth stocks. NIFTY means National Index for Fifty.