We present LANG-N-SEND, a π-calculus that is equipped with language definitions. Processes can define languages in operational semantics, and use them to execute programs. Furthermore, processes can send and receive pieces of operational semantics through channels.We present a reduction semantics for LANG-N-SEND, and we offer examples that demonstrate some of the scenarios that LANG-N-SEND captures.• A client that lets a server decide whether its language is synchronous or asynchronous by receiving the semantics of the output operator from the server.