Mo. Rev. Stat. § 143.101: Definitions.

1. "Resident" means an individual who is domiciled in this state, unless he (1) maintains no permanent place of abode in this state, (2) does maintain a permanent place of abode elsewhere, and (3) spends in the aggregate not more than thirty days of the taxable year in this state; or who is not domiciled in this state but maintains a permanent place of abode in this state and spends in the aggregate more than one hundred eighty-three days of the taxable year in this state.

2. "Nonresident" means an individual who is not a resident of this state.