14 CFR 1.3: Rules of construction.

(a) In this chapter, unless the context requires otherwise:

(1) Words importing the singular include the plural;

(2) Words importing the plural include the singular; and

(3) Words importing the masculine gender include the feminine.

(b) In this chapter, the word:

(1) Shall is used in an imperative sense;

(2) May is used in a permissive sense to state authority or permission to do the act prescribed, and the words “no person may * * *” or “a person may not * * *” mean that no person is required, authorized, or permitted to do the act prescribed; and

(3) Includes means “includes but is not limited to”.