(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.