Of all the annoying buzzwords, "functionality" is the worst when I am in the middle of writing a specification (as I am now): "these requirements define the functionality to be included in version 2"..."as part of the download functionality, we need to capture blah blah blah" (Don't get me started on "capture")
"Functionality" is too cumbersome, and makes it sound like you are trying to make something sound more important than it is. "Capability" works sometimes, and sometimes "function" itself works; "subsystem" might work at times too...but we need a simple word for the concept of "set of related functions", preferably in 3 syllables or less. Any suggestions?