common parameters

1. usually denotes the annual volatility of the log-return of the underlying security. It is always assumed to be positive.
2. usually denotes the annual interest rate earned in the domestic market.
3. usually denotes the annual interest rate earned in the foreign market. In case of a stock this can be interpreted as a continuously paid dividend rate.
4. usually denotes the correlation of the log-returns of two underlying securities.
5. T usually denotes the expiration time of the derivative security.
6. usually takes the value +1 in case of a call option and the value -1 in case of a put option.
7. K usually denotes the strike price.