I agree like many responses that there are really no right answers since these are just terms which can be varied depending on which Agile camp you are based on and you can definitely make up your own camp as long as everyone in your team including the external stakeholders understand what they mean. It is just a way of organizing your requirement.

The answer I like is from Mike Cohn's camp and it is fairly simple.

http://www.mountaingoatsoftware.com/blog/stories-epics-and-themes


Epic is just a big Story (hierarchical)
Theme is just a group of Stories (pretty much like tag)


He actually avoids the term "Feature". I assume that it is mainly because it was a common term in the traditional waterfall world. Many Agile camp tends to use different terms to emphasize the differences.

So in your PM's definition, Feature is somewhere in the middle of the Epic-Story hierarchy.

Here is my info-graphic of this definition from my InfoQ article http://www.infoq.com/articles/visualize-big-picture-agile ;-)



Relationship between user story, feature, and epic?
In the back of my mind, I'm almost certain there are at least several individual English word that means to punish one's self. It doesn't have to be physical, necessarily, but it must be some kind of self-punishment. Are there such words? Clinical words are also accepted (i.e. psychological terminology).
