A person who owns a unit in a multi-unit structure with an undivided interest in common elements would hold a:

In a multi-unit structure where an individual owns a unit alongside an undivided interest in common elements, that individual holds a condominium. This ownership structure allows the unit owner to have exclusive ownership of their individual unit while simultaneously sharing ownership of common areas with other unit owners, such as hallways, pools, and recreational facilities.

This arrangement is specifically designed to provide both private ownership and communal living, which is characteristic of condominiums. Unit owners are responsible for their own space and also contribute to the maintenance and upkeep of shared areas through association fees. This distinguishes condominiums from other types of ownership arrangements, such as cooperatives or time-share interests, which involve different legal and management structures.