14 CFR § 1.3

In this chapter, unless the context requires otherwise:

Words importing the singular include the plural;

Words importing the plural include the singular; and

Words importing the masculine gender include the feminine.

In this chapter, the word:

Shall is used in an imperative sense;

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

Includes means “includes but is not limited to”.