In respect to the time of enjoyment, an interest in property is either: (1) present or future; and (2) perpetual or limited.
Mont. Code Ann. § 70-1-315, under Kinds of Ownership Interests.
Mont. Code Ann. § 70-1-315
In respect to the time of enjoyment, an interest in property is either: (1) present or future; and (2) perpetual or limited.