When two or more persons own property collectively as if they were a single person, what is this called?

The concept described in the question refers to how two or more individuals can collectively own property as if they were one entity. This arrangement is known as joint tenancy.

In joint tenancy, all owners have an equal share in the property, and a key feature is the right of survivorship. This means that when one owner passes away, their share automatically transfers to the surviving owners rather than being passed down through an estate. This attribute creates a unified ownership experience, emphasizing that the property is treated as a single unit rather than as separate fractional interests.

While co-ownership can refer to various forms of property ownership among multiple parties, the specific mechanism by which joint tenancy operates, including equal shares and survivorship rights, distinguishes it as the correct answer in this context. Other ownership structures, like tenancy in common, do not confer the same rights and characteristics, particularly the right of survivorship, and thus would not accurately match the description.