If an owner's rights in an estate cannot be determined in duration, what type of estate do they own?

The correct answer is that the owner possesses a freehold estate when their rights in the estate cannot be determined in duration. A freehold estate is typically characterized by an indefinite duration, meaning it is owned for an undetermined period of time that could last for a lifetime or even beyond. This type of estate grants the owner a greater degree of control and a more substantial interest in the property compared to estates that are for fixed terms or limited durations.

In contrast, a leasehold estate is defined by a specific duration and is limited by the terms of the lease agreement. A life estate, while also a form of freehold estate, is explicitly limited to the duration of a person's life. Tenancy at will is a rental arrangement that lacks a definite duration and can be terminated by either party with proper notice, but this does not confer ownership rights to the estate in the same way a freehold estate does. Therefore, the indefiniteness of duration characterizes freehold estates as distinct from these other types of property interests.