It's common in web applications to serve several small applications, combined through domain routing, to a user as a single service. I could have separate application for login, profile management, and chat being served as:
It's a trivial example, but it serves its purpose. To the user, it's one website, but for developers, it's several small applications. This comes with plenty of advantages that mostly boil down to having a small codebase.
I'm beginning mobile development (react-native) and wondering if this pattern has found it's way into that environment? My hunch is "no" due to the type of deliverable. A mobile application is delivered as one thing to an app store where a website can be "composed" through URL mapping, but I also know developers are smart and I could be totally wrong.