S.D. Codified Laws § 34-20B-4

For the purposes of this chapter, unless the context otherwise requires, "precursor" or "immediate precursor" means a substance which the department has found to be and by regulation designates as being a principal compound commonly used or produced primarily for use, and which is an immediate chemical intermediary used or likely to be used, in the manufacture of a controlled drug or substance, the control of which is necessary to prevent, curtail, or limit such manufacture.