Originally from mathematics, the term describes a pattern where the identical code is shared between the frontend (client) and backend (server).

Isomorphic JavaScript that can run on both the client-side and the server-side. It’s the combination of server-side rendering and client-side rendering, combining the advantages of both. In an isomorphic application, the initial request made by a browser is processed by the server while any subsequent request is processed in/by the client.