Words used in the present tense include the future; the singular number includes the plural and the plural the singular; the word "person" includes a corporation as well as an individual; the word "lot" includes the word "plot." The term "occupied" or "used" as applied to any building shall be construed as though followed by the words "or intended, arranged or designed to be occupied or used." The word "shall" is mandatory and not optional. All other words used in this chapter shall carry their customary meanings.