Rough artworks that feel like I might/should continue working on them count as "sketches" in my book. Note that even a colored drawing may in that sense be a sketch. The idea is that if I had the opportunity, these drawings might get worked on further and turned into full artworks, but in their current state they are "discontinued", either because I was too busy to continue, or because I liked how they turned out in their current, sketchy state, and I felt like they achieved what I wanted them to without needing further elaboration. That last part kind of makes clear that the distinction between sketch and illustration is pretty vague. Even a quick drawing can count as a full, finished artwork if it looks the part.