Something is said to multipartite if it consists two or more distinct parts. If there are only two parts it is called bipartite, if there are three it is tripartite and something consisting of N parts is called N-partite.
In quantum information science it is often quantum systems that are shared between a number of parties, usually spatially separated and sometimes called Alice, Bob, Charlie, etc.
If the subsystems are described by the Hilbert spaces H1, H2, …, HN the compound multipartite system is described by the tensor product of the Hilbert spaces, H = H1 ⊗ H2 ⊗ … ⊗ HN. State vectors and density operators on H are called multipartite quantum states.
- Tripartite in Wiktionary