DISC is a financial function in Google Sheets that calculates the discount rate of a security, given the security's settlement date, maturity date, price, and redemption value. It is used to analyze and value bonds and other debt securities.

The syntax for the DISC function is as follows:

DISC(settlement, maturity, price, redemption, [daycountconvention])

settlement: The settlement date of the security, represented as a date or a reference to a cell containing a date. maturity: The maturity date of the security, represented as a date or a reference to a cell containing a date. price: The price at which the security is currently trading, per $100 face value. redemption: The redemption value of the security, per $100 face value. daycountconvention (optional): The day count convention to use in the calculation. This is an optional argument and can be omitted if not needed.

The DISC function returns the annual discount rate of the security as a decimal value.