92 Ill. Adm. Code 454.50
Rules of Construction
Section 454
Section 454.50 Rules of
Construction
a) In these Rules unless the context requires otherwise:
1) Words imparting the singular include the plural;
2) Words imparting the plural include the singular;
3) Words imparting the masculine gender include the feminine.
b) In these Rules, the word:
1) "Shall" is used in an imperative sense;
2) "Must" is used in an imperative sense;
3) "Should" is used in a recommendatory sense;
4) "May" is used in a permissive sense to state
authority or permission to do the act described and the words "no person
may *** " or "a person may not *** " means that no person is
required, authorized or permitted to do the act described; and
5) "Includes" is used as a word of inclusion not
limitation.