[Code of Federal Regulations] [Title 49, Volume 2] [Revised as of October 1, 2003] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR171.9] [Page 95-96] TITLE 49--TRANSPORTATION CHAPTER I--RESEARCH AND SPECIAL PROGRAMS ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PART 171_GENERAL INFORMATION, REGULATIONS, AND DEFINITIONS--Table of Contents Sec. 171.9 Rules of construction. (a) In this subchapter, unless the context requires otherwise: (1) Words imparting the singular include the plural; (2) Words imparting the plural include the singular; and (3) Words imparting the masculine gender include the feminine; (b) In this subchapter, 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 [[Page 96]] (5) ``Includes'' is used as a word of inclusion not limitation. [Amdt. 171-32, 41 FR 15996, Apr. 15, 1976, as amended by Amdt. 171-32A, 41 FR 40630, Sept. 20, 1976; Amdt. 171-121, 58 FR 51528, Oct. 1, 1993]