What term describes the ownership structure where all property is owned either in severalty or in concurrence?

The term that describes the ownership structure where all property is owned either in severalty or in concurrence is Concurrent Ownership. This concept refers to a situation in which two or more individuals hold an ownership interest in the same property concurrently. Various forms of concurrent ownership include joint tenancy, tenancy in common, and tenancy by the entireties. Each of these forms has specific legal implications regarding the relationship between the co-owners and their rights to the property.

The distinguishing feature of concurrent ownership is that it allows multiple parties to share ownership interests that can vary in scope and duration. For instance, in a tenancy in common, co-owners can have unequal shares, while joint tenants typically have equal shares along with the right of survivorship.

In contrast, the other choices refer to specific types of property interests that do not capture the broad concept of shared ownership. A Life Estate involves ownership for the duration of an individual's life but does not imply concurrent ownership with others. Fee Simple Absolute represents the highest form of ownership in real estate, without limitations on duration, and does not pertain to multiple owners. A Leasehold Estate pertains to a tenant's rights under a lease agreement, which is again distinct from ownership interests in property.