Rules of construction.

(a) In part 325 of subchapter A and in this subchapter, 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 present tense include the future tense. (b) In this subchapter the word— (1) Officer includes any person authorized by law to perform the duties of the office; (2) Shall is used in an imperative sense; (3) Must is used in an imperative sense; (4) Should is used in a recommendatory sense; (5) May is used in a permissive sense; and (6) Includes is used as a word of inclusion, not limitation. [53 FR 18052, May 19, 1988, as amended at 60 FR 38744, July 28, 1995; 83 FR 16226, Apr. 16, 2018]