Delta: A measure of the rate of change in an option's theoretical value for a one-unit change in the price of the underlying security. Call options have positive deltas, while put options have negative deltas. Technically, the delta is an instantaneous measure of the option's price change, so that the delta will be altered for even fractional changes by the underlying entity.

Position: The total of a trader's open contracts - the combined total of antrader's open option contracts (calls and/or puts) and long or short stock.