to C": B would have a vested remainder subject to divestment because he could be divested of his interest by an act of A before the interest becomes possessory. A future interest is vested subject to open if it belongs to a class of beneficiaries, where that class can expand. A common example is a grant from O "to A's children", where A is a man: the class of A's children can't be closed until approximately thirty eight weeks after A dies, so any children alive at the time of the grant are vested subject to open. This interest is also sometimes referred to as being vested subject to partial divestment. A person may divest themselves of, or alienate, only those interests that are guaranteed to vest. This rule aligns with the policy that a person should not be allowed to sell a thing that he or she does not own outright. Interests that are not guaranteed to vest are subject to the rule against perpetuities. Future interests in the transferor Reversion A reversion occurs when a granted estate is absolutely vested in the grantor. Example: "O grants Blackacre to A for life." Analysis (O): A is guaranteed to die (eventually), at which point Blackacre returns to O. This future interest is absolutely (indefeasibly) vested in O. Analysis (A): A has a life estate. Alienation: O can alienate her future interest. A can alienate his rights in the property, but only to the extent that those rights were granted him (i.e., as a life estate). So A can sell Blackacre to B, but once A dies it returns to O. Notice that B has no control over this kind of vesting. Reversion is not subject to the rule against perpetuities, because O's future interest is absolutely vested. Possibility of reverter There is a possibility of reverter when an estate will return to the grantor if a condition is violated. The possibility of reverter can only follow a fee simple determinable. Example: "O grants Blackacre to A as long as A refrains from drinking alcohol." Analysis: If A never drinks after the grant (and never sells the property), then Blackacre will belong to A at O's death, and be distributed according to the rules of probate. If A does drink after the grant, then the property returns to O. Language used: Durational. Examples include "for as long as", "while", and "during".