A market index of approximately 6,500 U.S. based equities traded on the American Stock Exchange, the New York Stock Exchange and the NASDAQ stock market.
To sell an option that is not owned through an opening sale transaction. While this position remains open, the writer is subject to fulfilling the obligations of that option contract; i.e., to sell stock (in the case of a call) or buy stock (in the case of a put) if that option is assigned.