Mo. Rev. Stat. § 1.030: Plural includes the singular — masculine includes feminine.

1. Whenever, in any statute, words importing the plural number are used in describing or referring to any matter, parties or persons, any single matter, party or person is included, although distributive words are not used.

2. When any subject matter, party or person is described or referred to by words importing the singular number or the masculine gender, several matters and persons, and females as well as males, and bodies corporate as well as individuals, are included.