A landlord-tenant relationship that arises because of some defect in a written lease or because the parties intended to execute a lease but,for some reason,never did.It continues for as long as both parties desire it to continue,usually on a month-to-month basis.Many consumer protection statutes require a minimum of 30 days notice before termination of a tenancy at will. (Do not confuse with a periodic tenancy, which may be from month to month and terminable upon a 30-day notice, but which was never intended to be anything more than a lease for an indefinite time.)