Code of Alabama
Article 8 - Remainders and Executory Devises.
Section 35-4-211 - Vested or Contingent Remainders Generally.

Remainders are either vested or contingent. A vested remainder is one limited to a certain person at a certain time or upon the happening of a necessary event. A contingent remainder is one limited to an uncertain person or upon an event which may or may not happen.