Assignment is a transfer of rights or duties under a contract. Rights may be assigned to a third party (called the assignee) unless the contract forbids it. Obligations also may be assigned (or delegated), but the original party remains primarily liable unless specifically released. An assignment may be made without the consent of the other party unless the contract includes a clause that permits or forbids assignment.
Substitution of a new contract for an existing contract is called novation. The new agreement may be between the same parties, or a new party may be substituted for (this is novation of the parties). The parties’ intent must be to discharge the old obligation.
Assignment – substitution of parties
Novation – substitution of contracts