What type of condo plan defines units by the structure itself?

The correct answer is the type of condo plan that defines units by the structure itself, which is conventional plans. In a conventional condo plan, the condominium units are defined by the physical structure and layout of the building, such as walls and floors, allowing for each unit to be owned separately. This is a traditional approach to delineating ownership within a multi-unit dwelling, emphasizing the specific dimensions and boundaries of each unit.

Conventional condo plans also typically include the common areas that are shared among the residents, which might encompass hallways, stairwells, and amenities. This structured definition helps clarify ownership rights, responsibilities, and the relationship between individual units and the shared spaces, making it clear for both owners and real estate professionals how the property is divided.

In contrast, options like bare land condo plans define units based on the land itself without a physical structure, while blended plans combine aspects of different condo types and fractional ownership plans involve shared ownership among multiple parties but do not relate to the structure definition. Thus, conventional plans are the most clearly defined structure-based ownership method among the provided choices.