Unity of possession
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
Joint possession of two rights by several titles, as where a lessee of land acquires the title in fee-simple, which extinguishes the lease. The term also describes one of the essential properties of a joint estate, each of the tenants having the entire possession as well of every parcel as of the whole.
2 Bl. Comm. 182.