SDCL § 54-3-1: Interest defined.

Interest is the compensation allowed by law for the use, or forbearance, or detention of money or its equivalent, including without limitation, points, loan origination fees, credit service or carrying charges, charges for unanticipated late payments, and any other charges, direct or indirect, as an incident to or as a condition of the extension of credit. These charges do not include charges made by a third party.