I think there's a lot of confusion about terminology in the requirements and business analysis space, even after all these years. Just this morning I found an article at iiba.org that says just what I show in the figure: "Epics are realized by Features. Features are realized by User Stories."

I would say the opposite of what you say: I think there could be multiple use cases within a single feature. Which then gets us back to the point of what level of abstraction we are talking about when we use these terms. It sounds like you're using the term "feature" to refer to what are more commonly called functional requirements, shown at the lowest level of abstraction in my figure. I define a feature as "one or more logically related system capabilities that provide value to a user and are described by a set of functional requirements."

I did not have space in this short article to go into detail about all these different terms. I discuss the various levels of abstraction on pages 111-112 of my latest book, "Software Requirements Essentials."

The fact that we do not have clear, agreed-upon definitions of such basic terms that people use all the time in business analysis is a sad commentary on the state of the industry.