What is Common Area?

Legal Definition
A common area is, in real estate or real property law, the "area which is available for use by more than one person..." The common areas are those that are available for common use by all tenants, (or) groups of tenants and their invitees.
-- Wikipedia
Legal Definition
A common area is, in real estate or real property law, the "area which is available for use by more than one person..." The common areas are those that are available for common use by all tenants, (or) groups of tenants and their invitees. In Texas and other parts of the United States, it is "An area inside a housing development that is owned by all residents or by an overall management structure which charges each tenant for maintenance and upkeep."

Common areas often exist in apartments, gated communities, condominiums, cooperatives and shopping malls.

In any situation where there is a tenancy in common, all the tenants in common collectively own the common areas, meaning that any one individual owner does not possess more control over the land than any other owner.

This differs from a commons or common land, as used in English law, which is owned by one person, but which may be used by a group of persons.
-- Wikipedia
Legal Definition
Any areas that are shared by others in the same building.