I believe words are important.¹ I recently caught myself saying something I consider dangerous for the way we think about computing and programming. I found my self saying “UI” (which is short for “User Interface”) to describe a “GUI” (a “Graphical User Interface”). UI is a broad category which encompasses multiple ways a user may interface with a system. A GUI is a specific instance of UI which relies on ‘visual metaphors’ to communicate information to a user and allow the user to interact with the underlying system (the most ubiquitous example of a GUI is a website).

When I use ‘UI’ to describe a GUI, I’m limiting the definition of UI only to GUIs.² Shrinking the definition of UI is dangerous because it makes it easy for us to forget about all of the other ways users interface with a system. A CLI (Command Line Interface) or API (Application Programming Interface) is just as much a UI as a GUI. All interfaces with a system should be as user-friendly as possible and the first step to accomplish this is to recognize all of the ways a user interfaces with a system.