Section 193.2009 - Rules of regulatory construction(a) As used in this part: (1) "Includes" means including but not limited to;(2) "May" means is permitted to or is authorized to;(3) "May not" means is not permitted to or is not authorized to; and(4) "Shall" or "must" is used in the mandatory and imperative sense.(b) In this part: (1) Words importing the singular include the plural; and(2) Words importing the plural include the singular.Wis. Admin. Code Department of Transportation § app 1 § 193.2009