Which estate allows for the possibility of reverting back to the original owner if conditions are not met?

The fee simple defeasible estate is characterized by certain conditions or limitations that, if violated, could result in the property reverting back to the original owner or grantor. This type of estate is distinguished by its conditional nature; the ownership of the property depends on the fulfilment of specific terms. For example, a property might be transferred to someone with the stipulation that it is used for educational purposes only. If that condition is not met—say, if the property is then used for industrial purposes—the original owner has the right to reclaim the property.

In contrast, a fee simple absolute grants full ownership without any conditions, which means it cannot revert to the original owner based on how the property is used. A life estate provides ownership for the duration of a specific person's life, after which the property typically passes to another designated party, but it also does not contain the specific reverting conditions present in a fee simple defeasible. Lastly, a leasehold estate concerns the rights of tenants and landlords and does not involve conditions that would lead to reversion back to a former owner. Thus, the nature of a fee simple defeasible estate is what solidifies it as the correct answer to this question.