kristallimeri said:
葉月 is the sketch fetishist here so he'll probably be thinking with his penis whenever he speaks on this subject.
Fixed. ;)
Seriously, though; sketch definitely should not be applied to all line art. We need a separate "line_art" tag for that, with a "lineart" alias.
"sketch" should be used for rough drawings; including, but not limited to, those used as a basis or study for a subsequent finished version.
Most sketches will probably be in pencil, but other media are possible too (pen, charcoal...). The defining factor is the roughness and/or the unfinished feeling.
A separate "pencil" tag could be added, covering all pencil drawings, even finished ones.
Clean, crisp lineart, especially if in ink, is not a sketch (unless it's obviously unfinished, eg it has construction lines or missing anatomy). Partial iterations of a picture are not necessarily sketches; for example, a crisply inked picture which is later colored is not a sketch; a partially colored but otherwise complete picture is not a sketch. Those could be tagged as "unfinished".