49 CFR §1500.5

1. (a)In this chapter, unless the context requires otherwise:
   1. (1)Words importing the singular include the plural.
   2. (2)Words importing the plural include the singular.
   3. (3)Words importing the masculine sex include the feminine.
2. (b)In this chapter, the word:
   1. (1)“Must” is used in an imperative sense;
   2. (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. (3)“Includes” means “includes but is not limited to”.