N.D. Cent. Code § 47-02-15: Future estates - Classification

A future interest is either vested or contingent. It is vested when there is a person in being who would have a right, defeasible or indefeasible, to the immediate possession of the property upon the ceasing of the intermediate or precedent interest. It is contingent while the person in whom or the event upon which it is limited to take effect remains uncertain.